Expert Interview

The high price of direct-acting antiviral (DAA) oral medications has made patient access challenging despite the availability of multiple effective treatment options for hepatitis C virus (HCV). Has there been any recent progress in making these treatments more affordable to patients? 

Dr. Jakab:  Certainly. We used to have great difficulty getting these medications to our patients, regardless of whether they were covered by private insurance or through the United States Department of Veterans Affairs (VA). The last few years have been amazing, not only in terms of availability of more regimens that are equally effective in curing HCV, but also in terms of patient access. I think this is capitalism at its best. Having competition—more regimens on the market—has helped drive the prices down.

These regimens are expensive, but very few patients actually pay the sticker price because the insurance plans end up negotiating a much better fee for a preferred regimen. The reality is considerably better now than it used to be even a few years ago, with more effective regimens available, and at an affordable price.

There is not much transparency in terms of pricing, so it is usually difficult to figure it out how much one insurance plan pays versus another. From the patient's perspective the progress is visible and translated in many patients being cured from HCV.

Have any of your patients faced other treatment access challenges unrelated to financial cost?

Dr. Jakab:  Historically, when the first DAAs became available, there were certain requirements put forward by insurance companies before these medications were approved given their high price at that time. Unfortunately, some of them are still in effect.

Providers still must document their clinical evaluation and laboratory testing before these medications get approved, which is important for clinical care, but some insurance plans will only cover HCV treatment for patients with advanced (stage 3 or 4) fibrosis.

Another requirement that pains me a lot—though again, great progress has been made—has to do with sobriety for patients who use drugs or alcohol. Some plans require 3 to 6 months of sobriety, or for the patient to be connected to a substance use disorder clinic or a relapse program.

There have also been some restrictions regarding which providers could prescribe these medications. Initially this was limited to hepatology, gastroenterology, or infectious disease specialists. Given the fact that the current DAA regimens are so easy to use due to their short duration of treatment and minimal side effects, more providers are comfortable with prescribing these medications. It certainly helps that CDC recommendations support the expansion of the provider pool to include primary care providers and substance use disorder providers. Physician assistants and APRNs have been increasingly involved in prescribing these medications as well. Pharmacists help us get the approval from the insurance companies, but PharmDs also treat many HCV patients.

Certain states are ahead of others in terms of eliminating Medicaid requirements that decrease patient access to HCV medications. I am lucky to be in Connecticut, which is one of the states where Medicaid restrictions have pretty much been lifted in terms of fibrosis staging or sobriety or prescriber requirements. This progress had a lot to do with patient and provider advocacy. Back in 2015 the New Haven Legal Assistance lobbied the state’s policymakers and Medicaid leadership to change these requirements. For patients covered by commercial insurance plans there are some requirements still in place, but overall, it is much better.

I have also witnessed the revolution of HCV treatment at the VA. A few years back we were restricting the use of these medications for patients with advanced fibrosis. Now the VA has all the available medications on the formulary, and there are no restrictions in terms of fibrosis staging, or sobriety requirements.

How has your team at the West Haven VA helped patients access HCV care through collaboration with other providers?

Dr. Jakab: It has been amazing to see how innovative people can be. It is true that if there is a will, there is a way. We finally had those medications so effective in curing HCV but were faced with challenges getting them to our patients. There was a huge effort throughout the VA, which is the national leader in the treatment of HCV, with more than 100,000 veterans cured. VA Connecticut was part of the movement: we expanded our liver clinic team to include a nurse practitioner, a PharmD, RN care coordinators, and a health psychologist. This way we could help our patients overcome many psychosocial or medical barriers and get them successfully treated.

The last step was going where the patients were. We realized that some patients who would benefit from treatment would not necessarily engage with us in liver clinic, even if they kept up with seeing their primary care physician. So instead of trying to get the patients into the liver clinic, we developed a program called HELP C, which stands for “HEpatitis C Leaders in Primary Care. The purpose of the program was to educate primary care providers interested in treating HCV. We continue to provide support for them through teleconferences or being available for any questions. This way we could indirectly treat patients with HCV without having them come to the liver clinic.

We also collaborated with our colleagues from substance use disorder clinics, to make sure they are updated in terms of ease of HCV treatment and need to screen for HCV in these high-risk patients.

Is there any other action that physicians can take to help improve HCV treatment accessibility for their patients?

Dr. Jakab: Education of patients, providers and policy makers is most important, and a lot of that responsibility is on those of us who are already helping patients to get to their HCV cure. It has to do with breaking barriers. Many providers still have misconceptions, for example, when it comes to patients who are actively using drugs. They feel that we should not spend resources on these patients because of their lack of engagement in terms of treatment of their substance use disorder and risk of relapse. However, we do have data proving that even patients who are actively injecting drugs achieve a high level of compliance with medications and a high level of cure in the range of 95% or so. Having the sobriety requirement on some insurance plans is a significant barrier to treatment, and it does not help select the patients who will successfully achieve HCV cure. All patients should be treated. In fact, by focusing on this high-risk category of patients, society benefits overall because by decreasing the HCV burden, we get closer to HCV eradication.

It is also important that the providers who are interested in treating HCV get familiar with the paperwork required to get these medications approved, also partnering with subspecialty pharmacies particularly when dealing with commercial insurances. In addition, there are assistance programs for patients who do not have insurance, or they are underinsured, or they get denied by their insurance plan. At the end of the day, helping a patient to get treated is worth the extra time spent with bureaucracy.

I would also encourage providers to continue looking for innovative approaches, and to try to develop multidisciplinary programs. Care coordination—partnering with pharmacy, psychology, and social work subspecialties—is what worked best for us at the West Haven VA. We were able to treat patients that were written off many times before; patients who suffered homelessness, struggled with medication adherence for their high blood pressure, or diabetes. They were patients about whom everybody said, “You guys are crazy. They will never get the treatment completed, never mind getting cured of HCV.” But they did—so it is all about advocating for your patients and partnering with the right people.

The high price of direct-acting antiviral (DAA) oral medications has made patient access challenging despite the availability of multiple effective treatment options for hepatitis C virus (HCV). Has there been any recent progress in making these treatments more affordable to patients? 

Dr. Jakab:  Certainly. We used to have great difficulty getting these medications to our patients, regardless of whether they were covered by private insurance or through the United States Department of Veterans Affairs (VA). The last few years have been amazing, not only in terms of availability of more regimens that are equally effective in curing HCV, but also in terms of patient access. I think this is capitalism at its best. Having competition—more regimens on the market—has helped drive the prices down.

These regimens are expensive, but very few patients actually pay the sticker price because the insurance plans end up negotiating a much better fee for a preferred regimen. The reality is considerably better now than it used to be even a few years ago, with more effective regimens available, and at an affordable price.

There is not much transparency in terms of pricing, so it is usually difficult to figure it out how much one insurance plan pays versus another. From the patient's perspective the progress is visible and translated in many patients being cured from HCV.

Have any of your patients faced other treatment access challenges unrelated to financial cost?

Dr. Jakab:  Historically, when the first DAAs became available, there were certain requirements put forward by insurance companies before these medications were approved given their high price at that time. Unfortunately, some of them are still in effect.

Providers still must document their clinical evaluation and laboratory testing before these medications get approved, which is important for clinical care, but some insurance plans will only cover HCV treatment for patients with advanced (stage 3 or 4) fibrosis.

Another requirement that pains me a lot—though again, great progress has been made—has to do with sobriety for patients who use drugs or alcohol. Some plans require 3 to 6 months of sobriety, or for the patient to be connected to a substance use disorder clinic or a relapse program.

There have also been some restrictions regarding which providers could prescribe these medications. Initially this was limited to hepatology, gastroenterology, or infectious disease specialists. Given the fact that the current DAA regimens are so easy to use due to their short duration of treatment and minimal side effects, more providers are comfortable with prescribing these medications. It certainly helps that CDC recommendations support the expansion of the provider pool to include primary care providers and substance use disorder providers. Physician assistants and APRNs have been increasingly involved in prescribing these medications as well. Pharmacists help us get the approval from the insurance companies, but PharmDs also treat many HCV patients.

Certain states are ahead of others in terms of eliminating Medicaid requirements that decrease patient access to HCV medications. I am lucky to be in Connecticut, which is one of the states where Medicaid restrictions have pretty much been lifted in terms of fibrosis staging or sobriety or prescriber requirements. This progress had a lot to do with patient and provider advocacy. Back in 2015 the New Haven Legal Assistance lobbied the state’s policymakers and Medicaid leadership to change these requirements. For patients covered by commercial insurance plans there are some requirements still in place, but overall, it is much better.

I have also witnessed the revolution of HCV treatment at the VA. A few years back we were restricting the use of these medications for patients with advanced fibrosis. Now the VA has all the available medications on the formulary, and there are no restrictions in terms of fibrosis staging, or sobriety requirements.

How has your team at the West Haven VA helped patients access HCV care through collaboration with other providers?

Dr. Jakab: It has been amazing to see how innovative people can be. It is true that if there is a will, there is a way. We finally had those medications so effective in curing HCV but were faced with challenges getting them to our patients. There was a huge effort throughout the VA, which is the national leader in the treatment of HCV, with more than 100,000 veterans cured. VA Connecticut was part of the movement: we expanded our liver clinic team to include a nurse practitioner, a PharmD, RN care coordinators, and a health psychologist. This way we could help our patients overcome many psychosocial or medical barriers and get them successfully treated.

The last step was going where the patients were. We realized that some patients who would benefit from treatment would not necessarily engage with us in liver clinic, even if they kept up with seeing their primary care physician. So instead of trying to get the patients into the liver clinic, we developed a program called HELP C, which stands for “HEpatitis C Leaders in Primary Care. The purpose of the program was to educate primary care providers interested in treating HCV. We continue to provide support for them through teleconferences or being available for any questions. This way we could indirectly treat patients with HCV without having them come to the liver clinic.

We also collaborated with our colleagues from substance use disorder clinics, to make sure they are updated in terms of ease of HCV treatment and need to screen for HCV in these high-risk patients.

Is there any other action that physicians can take to help improve HCV treatment accessibility for their patients?

Dr. Jakab: Education of patients, providers and policy makers is most important, and a lot of that responsibility is on those of us who are already helping patients to get to their HCV cure. It has to do with breaking barriers. Many providers still have misconceptions, for example, when it comes to patients who are actively using drugs. They feel that we should not spend resources on these patients because of their lack of engagement in terms of treatment of their substance use disorder and risk of relapse. However, we do have data proving that even patients who are actively injecting drugs achieve a high level of compliance with medications and a high level of cure in the range of 95% or so. Having the sobriety requirement on some insurance plans is a significant barrier to treatment, and it does not help select the patients who will successfully achieve HCV cure. All patients should be treated. In fact, by focusing on this high-risk category of patients, society benefits overall because by decreasing the HCV burden, we get closer to HCV eradication.

It is also important that the providers who are interested in treating HCV get familiar with the paperwork required to get these medications approved, also partnering with subspecialty pharmacies particularly when dealing with commercial insurances. In addition, there are assistance programs for patients who do not have insurance, or they are underinsured, or they get denied by their insurance plan. At the end of the day, helping a patient to get treated is worth the extra time spent with bureaucracy.

I would also encourage providers to continue looking for innovative approaches, and to try to develop multidisciplinary programs. Care coordination—partnering with pharmacy, psychology, and social work subspecialties—is what worked best for us at the West Haven VA. We were able to treat patients that were written off many times before; patients who suffered homelessness, struggled with medication adherence for their high blood pressure, or diabetes. They were patients about whom everybody said, “You guys are crazy. They will never get the treatment completed, never mind getting cured of HCV.” But they did—so it is all about advocating for your patients and partnering with the right people.

The high price of direct-acting antiviral (DAA) oral medications has made patient access challenging despite the availability of multiple effective treatment options for hepatitis C virus (HCV). Has there been any recent progress in making these treatments more affordable to patients? 

Dr. Jakab:  Certainly. We used to have great difficulty getting these medications to our patients, regardless of whether they were covered by private insurance or through the United States Department of Veterans Affairs (VA). The last few years have been amazing, not only in terms of availability of more regimens that are equally effective in curing HCV, but also in terms of patient access. I think this is capitalism at its best. Having competition—more regimens on the market—has helped drive the prices down.

These regimens are expensive, but very few patients actually pay the sticker price because the insurance plans end up negotiating a much better fee for a preferred regimen. The reality is considerably better now than it used to be even a few years ago, with more effective regimens available, and at an affordable price.

There is not much transparency in terms of pricing, so it is usually difficult to figure it out how much one insurance plan pays versus another. From the patient's perspective the progress is visible and translated in many patients being cured from HCV.

Have any of your patients faced other treatment access challenges unrelated to financial cost?

Dr. Jakab:  Historically, when the first DAAs became available, there were certain requirements put forward by insurance companies before these medications were approved given their high price at that time. Unfortunately, some of them are still in effect.

Providers still must document their clinical evaluation and laboratory testing before these medications get approved, which is important for clinical care, but some insurance plans will only cover HCV treatment for patients with advanced (stage 3 or 4) fibrosis.

Another requirement that pains me a lot—though again, great progress has been made—has to do with sobriety for patients who use drugs or alcohol. Some plans require 3 to 6 months of sobriety, or for the patient to be connected to a substance use disorder clinic or a relapse program.

There have also been some restrictions regarding which providers could prescribe these medications. Initially this was limited to hepatology, gastroenterology, or infectious disease specialists. Given the fact that the current DAA regimens are so easy to use due to their short duration of treatment and minimal side effects, more providers are comfortable with prescribing these medications. It certainly helps that CDC recommendations support the expansion of the provider pool to include primary care providers and substance use disorder providers. Physician assistants and APRNs have been increasingly involved in prescribing these medications as well. Pharmacists help us get the approval from the insurance companies, but PharmDs also treat many HCV patients.

Certain states are ahead of others in terms of eliminating Medicaid requirements that decrease patient access to HCV medications. I am lucky to be in Connecticut, which is one of the states where Medicaid restrictions have pretty much been lifted in terms of fibrosis staging or sobriety or prescriber requirements. This progress had a lot to do with patient and provider advocacy. Back in 2015 the New Haven Legal Assistance lobbied the state’s policymakers and Medicaid leadership to change these requirements. For patients covered by commercial insurance plans there are some requirements still in place, but overall, it is much better.

I have also witnessed the revolution of HCV treatment at the VA. A few years back we were restricting the use of these medications for patients with advanced fibrosis. Now the VA has all the available medications on the formulary, and there are no restrictions in terms of fibrosis staging, or sobriety requirements.

How has your team at the West Haven VA helped patients access HCV care through collaboration with other providers?

Dr. Jakab: It has been amazing to see how innovative people can be. It is true that if there is a will, there is a way. We finally had those medications so effective in curing HCV but were faced with challenges getting them to our patients. There was a huge effort throughout the VA, which is the national leader in the treatment of HCV, with more than 100,000 veterans cured. VA Connecticut was part of the movement: we expanded our liver clinic team to include a nurse practitioner, a PharmD, RN care coordinators, and a health psychologist. This way we could help our patients overcome many psychosocial or medical barriers and get them successfully treated.

The last step was going where the patients were. We realized that some patients who would benefit from treatment would not necessarily engage with us in liver clinic, even if they kept up with seeing their primary care physician. So instead of trying to get the patients into the liver clinic, we developed a program called HELP C, which stands for “HEpatitis C Leaders in Primary Care. The purpose of the program was to educate primary care providers interested in treating HCV. We continue to provide support for them through teleconferences or being available for any questions. This way we could indirectly treat patients with HCV without having them come to the liver clinic.

We also collaborated with our colleagues from substance use disorder clinics, to make sure they are updated in terms of ease of HCV treatment and need to screen for HCV in these high-risk patients.

Is there any other action that physicians can take to help improve HCV treatment accessibility for their patients?

Dr. Jakab: Education of patients, providers and policy makers is most important, and a lot of that responsibility is on those of us who are already helping patients to get to their HCV cure. It has to do with breaking barriers. Many providers still have misconceptions, for example, when it comes to patients who are actively using drugs. They feel that we should not spend resources on these patients because of their lack of engagement in terms of treatment of their substance use disorder and risk of relapse. However, we do have data proving that even patients who are actively injecting drugs achieve a high level of compliance with medications and a high level of cure in the range of 95% or so. Having the sobriety requirement on some insurance plans is a significant barrier to treatment, and it does not help select the patients who will successfully achieve HCV cure. All patients should be treated. In fact, by focusing on this high-risk category of patients, society benefits overall because by decreasing the HCV burden, we get closer to HCV eradication.

It is also important that the providers who are interested in treating HCV get familiar with the paperwork required to get these medications approved, also partnering with subspecialty pharmacies particularly when dealing with commercial insurances. In addition, there are assistance programs for patients who do not have insurance, or they are underinsured, or they get denied by their insurance plan. At the end of the day, helping a patient to get treated is worth the extra time spent with bureaucracy.

I would also encourage providers to continue looking for innovative approaches, and to try to develop multidisciplinary programs. Care coordination—partnering with pharmacy, psychology, and social work subspecialties—is what worked best for us at the West Haven VA. We were able to treat patients that were written off many times before; patients who suffered homelessness, struggled with medication adherence for their high blood pressure, or diabetes. They were patients about whom everybody said, “You guys are crazy. They will never get the treatment completed, never mind getting cured of HCV.” But they did—so it is all about advocating for your patients and partnering with the right people.

Why has deep brain stimulation (DBS) surpassed ablative surgery as the surgical treatment of choice in patients with levodopa-induced dyskinesia (LID)?

Dr. LeWitt: In ablative surgery for LID, a thermo-coagulation lesion is placed in the globus pallidus interna (GPi). This target of therapy was in use before development of DBS as another way to treat involuntary movements complicating control of Parkinson disease with dopaminergic therapy.
 
The use of DBS has replaced ablative surgery in most centers offering functional neurosurgery because DBS offers far more control of the clinical outcome. The lesion created by ablation is a permanent effect, whether desired or not. If a GPi lesion were to be inaccurately placed, or too small or large, there could be consequences that a patient would have to live with. Furthermore, ablative surgery also had an unacceptably high incidence of dysphagia and dysarthria (speaking and swallowing difficulties) when the pallidotomy procedure was carried out bilaterally. Bilateral DBS can sometimes lead to similar problems, but by adjusting stimulation settings (or even shutting off one pulse generator when a patient is feeding or speaking), such outcomes can be avoided. With some of the stimulation devices currently in use, the DBS implanted pulse generator has an option for multiple stimulation settings to be created.

Most patients with Parkinson disease have bilateral involvement and so need both sides of the brain treated for optimal outcomes. Once DBS became available, pallidotomy carried out bilaterally was recognized to pose unacceptable risks for most patients.
 
The efficacy of DBS targeted at the GPi also seems to be better than the clinical results of pallidotomy in the earlier era of functional neurosurgery. Being able to change parameters of electrical stimulation (its location, frequency, pulse width, and current delivery) gives the clinician several tools for enhancing precision to tailor clinical effect and in a manner not achieved from pallidotomy. In the United States and elsewhere, electrical stimulation of GPi and other brain targets is the predominant procedure of functional neurosurgery for movement disorders.

Are there situations where ablative surgery is still considered, and if so, what are they?

Dr. LeWitt: Abblative neurosurgery is not widely used in the U.S. or Europe for movement disorders, though it might be utilized in clinical settings where the expensive DBS electrodes and pulse generators are not routinely available. Furthermore, there are patients who have MRI-incompatible situations and who might opt for lesioning the brain for LID (especially is carried out unilaterally)  In my experience at a U.S. hospital, these cases are currently quite rare since the risks of a thermoablation would seem to be greater than simply implanting an electrode in the brain.

Magnetic resonance-guided focused ultrasound (MRg-FUS) pallidotomy has emerged as an incisionless ablative technique. What are the pros and cons of that treatment?
 
Dr. LeWitt: Using MRg-FUS to create ablative lesions in the brain is a promising new direction for accomplishing an outcome of pallidotomy without the need to penetrate the skull and brain surgically. However, not many treatment centers have acquired equipment for this procedure.
 
The precision of localizing thermal ablations with FUS seems to be much improved over the operative surgical approach – this is because there's real-time MRI guidance that permit the clinician to localize the intended lesion. The methodology of FUS permits good control over the size of the thermocoagulation procedure carried out in the awake patient, who is able to report on any adverse aspects of the localization of the intended lesioning. Whether this new way to achieve pallidotomy will be an improvement over the conventional surgical methods, or whether this procedure (carried out unilaterally) will be equal to DBS outcomes, remains to be studied further.
 
In the best of scenarios, incisionless surgery will have fewer surgery-associated risks. By avoiding the need for devices that have to be inserted in the brain (and the risks and costs that they impose), that's an appealing prospect for future therapeutics of movement disorders like LID.

What do you believe will be the preferred surgical procedure for LID in the future?
 

Dr. LeWitt: Thanks to the long experience with DBS of the GPi and the other benefits this technique provides for control of Parkinson disease, I predict that implanted stimulation electrodes will continue to be a predominant treatment option. As an alternative approach, MRg-FUS is currently limited to unilateral use and has far less long-term clinical experience – it  should be regarded as still in the developmental stage (and is not an FDA-approved use, even though MRg-FUS use for treating tremor through thalamic lesioning is sanctioned). However, with more research experience and, if safe and effective, its ultimate approval, non-surgical GPi lesioning might become an appealing alternative to DBS. Research with GPi MRg-FUS has already had peer-reviewing reporting as to safety and efficacy. Of course, other options for control of LID are being explored, such as more constant delivery of levodopa and drugs specifically targeting mechanisms of involuntary movements.

Why has deep brain stimulation (DBS) surpassed ablative surgery as the surgical treatment of choice in patients with levodopa-induced dyskinesia (LID)?

Dr. LeWitt: In ablative surgery for LID, a thermo-coagulation lesion is placed in the globus pallidus interna (GPi). This target of therapy was in use before development of DBS as another way to treat involuntary movements complicating control of Parkinson disease with dopaminergic therapy.
 
The use of DBS has replaced ablative surgery in most centers offering functional neurosurgery because DBS offers far more control of the clinical outcome. The lesion created by ablation is a permanent effect, whether desired or not. If a GPi lesion were to be inaccurately placed, or too small or large, there could be consequences that a patient would have to live with. Furthermore, ablative surgery also had an unacceptably high incidence of dysphagia and dysarthria (speaking and swallowing difficulties) when the pallidotomy procedure was carried out bilaterally. Bilateral DBS can sometimes lead to similar problems, but by adjusting stimulation settings (or even shutting off one pulse generator when a patient is feeding or speaking), such outcomes can be avoided. With some of the stimulation devices currently in use, the DBS implanted pulse generator has an option for multiple stimulation settings to be created.

Most patients with Parkinson disease have bilateral involvement and so need both sides of the brain treated for optimal outcomes. Once DBS became available, pallidotomy carried out bilaterally was recognized to pose unacceptable risks for most patients.
 
The efficacy of DBS targeted at the GPi also seems to be better than the clinical results of pallidotomy in the earlier era of functional neurosurgery. Being able to change parameters of electrical stimulation (its location, frequency, pulse width, and current delivery) gives the clinician several tools for enhancing precision to tailor clinical effect and in a manner not achieved from pallidotomy. In the United States and elsewhere, electrical stimulation of GPi and other brain targets is the predominant procedure of functional neurosurgery for movement disorders.

Are there situations where ablative surgery is still considered, and if so, what are they?

Dr. LeWitt: Abblative neurosurgery is not widely used in the U.S. or Europe for movement disorders, though it might be utilized in clinical settings where the expensive DBS electrodes and pulse generators are not routinely available. Furthermore, there are patients who have MRI-incompatible situations and who might opt for lesioning the brain for LID (especially is carried out unilaterally)  In my experience at a U.S. hospital, these cases are currently quite rare since the risks of a thermoablation would seem to be greater than simply implanting an electrode in the brain.

Magnetic resonance-guided focused ultrasound (MRg-FUS) pallidotomy has emerged as an incisionless ablative technique. What are the pros and cons of that treatment?
 
Dr. LeWitt: Using MRg-FUS to create ablative lesions in the brain is a promising new direction for accomplishing an outcome of pallidotomy without the need to penetrate the skull and brain surgically. However, not many treatment centers have acquired equipment for this procedure.
 
The precision of localizing thermal ablations with FUS seems to be much improved over the operative surgical approach – this is because there's real-time MRI guidance that permit the clinician to localize the intended lesion. The methodology of FUS permits good control over the size of the thermocoagulation procedure carried out in the awake patient, who is able to report on any adverse aspects of the localization of the intended lesioning. Whether this new way to achieve pallidotomy will be an improvement over the conventional surgical methods, or whether this procedure (carried out unilaterally) will be equal to DBS outcomes, remains to be studied further.
 
In the best of scenarios, incisionless surgery will have fewer surgery-associated risks. By avoiding the need for devices that have to be inserted in the brain (and the risks and costs that they impose), that's an appealing prospect for future therapeutics of movement disorders like LID.

What do you believe will be the preferred surgical procedure for LID in the future?
 

Dr. LeWitt: Thanks to the long experience with DBS of the GPi and the other benefits this technique provides for control of Parkinson disease, I predict that implanted stimulation electrodes will continue to be a predominant treatment option. As an alternative approach, MRg-FUS is currently limited to unilateral use and has far less long-term clinical experience – it  should be regarded as still in the developmental stage (and is not an FDA-approved use, even though MRg-FUS use for treating tremor through thalamic lesioning is sanctioned). However, with more research experience and, if safe and effective, its ultimate approval, non-surgical GPi lesioning might become an appealing alternative to DBS. Research with GPi MRg-FUS has already had peer-reviewing reporting as to safety and efficacy. Of course, other options for control of LID are being explored, such as more constant delivery of levodopa and drugs specifically targeting mechanisms of involuntary movements.

Why has deep brain stimulation (DBS) surpassed ablative surgery as the surgical treatment of choice in patients with levodopa-induced dyskinesia (LID)?

Dr. LeWitt: In ablative surgery for LID, a thermo-coagulation lesion is placed in the globus pallidus interna (GPi). This target of therapy was in use before development of DBS as another way to treat involuntary movements complicating control of Parkinson disease with dopaminergic therapy.
 
The use of DBS has replaced ablative surgery in most centers offering functional neurosurgery because DBS offers far more control of the clinical outcome. The lesion created by ablation is a permanent effect, whether desired or not. If a GPi lesion were to be inaccurately placed, or too small or large, there could be consequences that a patient would have to live with. Furthermore, ablative surgery also had an unacceptably high incidence of dysphagia and dysarthria (speaking and swallowing difficulties) when the pallidotomy procedure was carried out bilaterally. Bilateral DBS can sometimes lead to similar problems, but by adjusting stimulation settings (or even shutting off one pulse generator when a patient is feeding or speaking), such outcomes can be avoided. With some of the stimulation devices currently in use, the DBS implanted pulse generator has an option for multiple stimulation settings to be created.

Most patients with Parkinson disease have bilateral involvement and so need both sides of the brain treated for optimal outcomes. Once DBS became available, pallidotomy carried out bilaterally was recognized to pose unacceptable risks for most patients.
 
The efficacy of DBS targeted at the GPi also seems to be better than the clinical results of pallidotomy in the earlier era of functional neurosurgery. Being able to change parameters of electrical stimulation (its location, frequency, pulse width, and current delivery) gives the clinician several tools for enhancing precision to tailor clinical effect and in a manner not achieved from pallidotomy. In the United States and elsewhere, electrical stimulation of GPi and other brain targets is the predominant procedure of functional neurosurgery for movement disorders.

Are there situations where ablative surgery is still considered, and if so, what are they?

Dr. LeWitt: Abblative neurosurgery is not widely used in the U.S. or Europe for movement disorders, though it might be utilized in clinical settings where the expensive DBS electrodes and pulse generators are not routinely available. Furthermore, there are patients who have MRI-incompatible situations and who might opt for lesioning the brain for LID (especially is carried out unilaterally)  In my experience at a U.S. hospital, these cases are currently quite rare since the risks of a thermoablation would seem to be greater than simply implanting an electrode in the brain.

Magnetic resonance-guided focused ultrasound (MRg-FUS) pallidotomy has emerged as an incisionless ablative technique. What are the pros and cons of that treatment?
 
Dr. LeWitt: Using MRg-FUS to create ablative lesions in the brain is a promising new direction for accomplishing an outcome of pallidotomy without the need to penetrate the skull and brain surgically. However, not many treatment centers have acquired equipment for this procedure.
 
The precision of localizing thermal ablations with FUS seems to be much improved over the operative surgical approach – this is because there's real-time MRI guidance that permit the clinician to localize the intended lesion. The methodology of FUS permits good control over the size of the thermocoagulation procedure carried out in the awake patient, who is able to report on any adverse aspects of the localization of the intended lesioning. Whether this new way to achieve pallidotomy will be an improvement over the conventional surgical methods, or whether this procedure (carried out unilaterally) will be equal to DBS outcomes, remains to be studied further.
 
In the best of scenarios, incisionless surgery will have fewer surgery-associated risks. By avoiding the need for devices that have to be inserted in the brain (and the risks and costs that they impose), that's an appealing prospect for future therapeutics of movement disorders like LID.

What do you believe will be the preferred surgical procedure for LID in the future?
 

Dr. LeWitt: Thanks to the long experience with DBS of the GPi and the other benefits this technique provides for control of Parkinson disease, I predict that implanted stimulation electrodes will continue to be a predominant treatment option. As an alternative approach, MRg-FUS is currently limited to unilateral use and has far less long-term clinical experience – it  should be regarded as still in the developmental stage (and is not an FDA-approved use, even though MRg-FUS use for treating tremor through thalamic lesioning is sanctioned). However, with more research experience and, if safe and effective, its ultimate approval, non-surgical GPi lesioning might become an appealing alternative to DBS. Research with GPi MRg-FUS has already had peer-reviewing reporting as to safety and efficacy. Of course, other options for control of LID are being explored, such as more constant delivery of levodopa and drugs specifically targeting mechanisms of involuntary movements.

recently coauthored the manuscript "Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia."* We took a moment to sit down with Mr. Martini to discuss some of the potential therapies for patients with Parkinson disease (PD).

How can targeting serotonergic neurons help control levodopa-induced dyskinesia (LID)?
 
Serotonergic neurons appear to have an interesting relationship with dyskinesia in patients with PD. One potential reason for this might be because the serotonergic neurons possess the molecular machinery to convert L-dopa into dopamine, contributing to dopaminergic transmission in the brain.
 
However, dopaminergic neurons possess auto receptors, which essentially act as an off switch when too much dopamine is being transmitted. This negative feedback loop works to stabilize dopaminergic transmission.
 
When a patient with early PD takes an oral dose of L-dopa, it is converted into dopamine in the central serotonergic neurons and the excess dopamine is buffered by retained dopaminergic neurons.
 
As PD advances, more significant destruction of these dopaminergic terminals means a loss in the capacity to buffer excess dopamine, which in turn can lead to dyskinesia.
 
I believe that there are particularly exciting results in preclinical and clinical studies exploiting this framework. For example, we have learned that there is a synergistic effect on dyskinesia reduction that occurs when agonists of 5-HT1A and 1B receptors are administered to animal models of PD. 
 
This presumably occurs because the serotonergic autoreceptors are being stimulated by the serotonin agonists. This may explain why previous studies using sarizotan, which is only a 5-HT1A agonist, did not show significant LID reduction. More recent clinical studies have taken advantage of this synergistic effect by giving eltoprazine, which is a dual 5-HT1A/1B agonist. Clinical trials with eltoprazine showed significant reduction in LID symptoms on two different clinical scales—the Clinical Dyskinesia Rating Scale and the Rush Dyskinesia Rating Scale.
 
You also discussed alpha-lipoic acid as a treatment option. How can this work to delay the onset of LID?
 
 Alpha-lipoic acid research revolves around the central finding that patients treated with L-dopa have been shown to have enhanced processes of oxidative stress occurring in their brains. 
 
There are a few possible reasons for this reaction. It might be that these patients have lower antioxidant levels or excessive oxidation of dopamine or disruptions in the mitochondrial transport chain. 
 
Other studies have found increased markers of oxidation and neuroinflammation present, which may suggest that monitoring these oxidative stress markers could be useful in some patients with PD who are receiving L-dopa. 
 
Some early studies found that alpha-lipoic acid could reduce reactive oxygen species and spare dopaminergic neurons in primate models of PD.
 
Recently we found more promising results when administering alpha-lipoic acid with L-dopa. Co-treatment had a dose-dependent anti-dyskinetic effect. 
 
When sampling of biomarkers and metabolites was done, the results corroborated the idea that alpha-lipoic acid might reduce oxidative stress and apoptosis to achieve neuroprotection.
 
It is also important to note this distinction with alpha-lipoic acid: among experimental Parkinson therapeutics it might be a disease-modifying agent. This is noteworthy when considering that most other therapies are simply just trying to alleviate symptoms of PD and dyskinesia.
 
More work still needs to be done in this area, including full-scale clinical studies to substantiate these claims in humans. But I do believe that the results to date are exciting. 
 
What other pharmacological approaches to LID look promising?
 
 There is another approach to LID that I believe to be promising, even though it is still a ways off from being clinically developed—it relates to beta-arrestin signaling.
 
Recent studies have elucidated that in addition to their roles as G-protein coupled receptors, dopamine receptors are also capable of signaling through a distinct beta-arrestin2-dependent pathway, in addition to the canonical G-protein pathway.
 
This is important because a lot of traditional dopamine agonists, including L-dopa, signal through dopamine D1/D2 receptors.
 
Other studies have also suggested that this G-protein independent pathway, the beta-arrestin pathway, along with traditional G-protein pathway, are important in regulating downstream responses at dopamine receptors. They play significant roles in converting dopamine signaling into motor function, which sheds new light on the known functions of beta-arrestins.
 
Some promising and exciting preclinical data has emerged, suggesting that beta-arrestin signaling is critical for locomotion in L-dopa and that when it is removed, locomotor responses to L-dopa are decreased and there is an increased propensity towards LID in these models.
 
Further validation for targeting beta-arrestin signaling at the dopamine receptors was provided in primate models of PD, where genetic overexpression of beta-arrestin reduced dyskinesias and rescued locomotion when L-dopa was given. 
 
I think we are at an exciting point in terms of the number of promising avenues that we have in devising potential strategies for treating LID. I think that innovations in this area have progressed significantly in recent years and I hope that at least a few of these experimental therapies might end up helping patients in the future.
 
*Martini ML, Neifert SN, Mocco J, et al. Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia. J Mov Disord. 2019;12
 

recently coauthored the manuscript "Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia."* We took a moment to sit down with Mr. Martini to discuss some of the potential therapies for patients with Parkinson disease (PD).

How can targeting serotonergic neurons help control levodopa-induced dyskinesia (LID)?
 
Serotonergic neurons appear to have an interesting relationship with dyskinesia in patients with PD. One potential reason for this might be because the serotonergic neurons possess the molecular machinery to convert L-dopa into dopamine, contributing to dopaminergic transmission in the brain.
 
However, dopaminergic neurons possess auto receptors, which essentially act as an off switch when too much dopamine is being transmitted. This negative feedback loop works to stabilize dopaminergic transmission.
 
When a patient with early PD takes an oral dose of L-dopa, it is converted into dopamine in the central serotonergic neurons and the excess dopamine is buffered by retained dopaminergic neurons.
 
As PD advances, more significant destruction of these dopaminergic terminals means a loss in the capacity to buffer excess dopamine, which in turn can lead to dyskinesia.
 
I believe that there are particularly exciting results in preclinical and clinical studies exploiting this framework. For example, we have learned that there is a synergistic effect on dyskinesia reduction that occurs when agonists of 5-HT1A and 1B receptors are administered to animal models of PD. 
 
This presumably occurs because the serotonergic autoreceptors are being stimulated by the serotonin agonists. This may explain why previous studies using sarizotan, which is only a 5-HT1A agonist, did not show significant LID reduction. More recent clinical studies have taken advantage of this synergistic effect by giving eltoprazine, which is a dual 5-HT1A/1B agonist. Clinical trials with eltoprazine showed significant reduction in LID symptoms on two different clinical scales—the Clinical Dyskinesia Rating Scale and the Rush Dyskinesia Rating Scale.
 
You also discussed alpha-lipoic acid as a treatment option. How can this work to delay the onset of LID?
 
 Alpha-lipoic acid research revolves around the central finding that patients treated with L-dopa have been shown to have enhanced processes of oxidative stress occurring in their brains. 
 
There are a few possible reasons for this reaction. It might be that these patients have lower antioxidant levels or excessive oxidation of dopamine or disruptions in the mitochondrial transport chain. 
 
Other studies have found increased markers of oxidation and neuroinflammation present, which may suggest that monitoring these oxidative stress markers could be useful in some patients with PD who are receiving L-dopa. 
 
Some early studies found that alpha-lipoic acid could reduce reactive oxygen species and spare dopaminergic neurons in primate models of PD.
 
Recently we found more promising results when administering alpha-lipoic acid with L-dopa. Co-treatment had a dose-dependent anti-dyskinetic effect. 
 
When sampling of biomarkers and metabolites was done, the results corroborated the idea that alpha-lipoic acid might reduce oxidative stress and apoptosis to achieve neuroprotection.
 
It is also important to note this distinction with alpha-lipoic acid: among experimental Parkinson therapeutics it might be a disease-modifying agent. This is noteworthy when considering that most other therapies are simply just trying to alleviate symptoms of PD and dyskinesia.
 
More work still needs to be done in this area, including full-scale clinical studies to substantiate these claims in humans. But I do believe that the results to date are exciting. 
 
What other pharmacological approaches to LID look promising?
 
 There is another approach to LID that I believe to be promising, even though it is still a ways off from being clinically developed—it relates to beta-arrestin signaling.
 
Recent studies have elucidated that in addition to their roles as G-protein coupled receptors, dopamine receptors are also capable of signaling through a distinct beta-arrestin2-dependent pathway, in addition to the canonical G-protein pathway.
 
This is important because a lot of traditional dopamine agonists, including L-dopa, signal through dopamine D1/D2 receptors.
 
Other studies have also suggested that this G-protein independent pathway, the beta-arrestin pathway, along with traditional G-protein pathway, are important in regulating downstream responses at dopamine receptors. They play significant roles in converting dopamine signaling into motor function, which sheds new light on the known functions of beta-arrestins.
 
Some promising and exciting preclinical data has emerged, suggesting that beta-arrestin signaling is critical for locomotion in L-dopa and that when it is removed, locomotor responses to L-dopa are decreased and there is an increased propensity towards LID in these models.
 
Further validation for targeting beta-arrestin signaling at the dopamine receptors was provided in primate models of PD, where genetic overexpression of beta-arrestin reduced dyskinesias and rescued locomotion when L-dopa was given. 
 
I think we are at an exciting point in terms of the number of promising avenues that we have in devising potential strategies for treating LID. I think that innovations in this area have progressed significantly in recent years and I hope that at least a few of these experimental therapies might end up helping patients in the future.
 
*Martini ML, Neifert SN, Mocco J, et al. Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia. J Mov Disord. 2019;12
 

recently coauthored the manuscript "Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia."* We took a moment to sit down with Mr. Martini to discuss some of the potential therapies for patients with Parkinson disease (PD).

How can targeting serotonergic neurons help control levodopa-induced dyskinesia (LID)?
 
Serotonergic neurons appear to have an interesting relationship with dyskinesia in patients with PD. One potential reason for this might be because the serotonergic neurons possess the molecular machinery to convert L-dopa into dopamine, contributing to dopaminergic transmission in the brain.
 
However, dopaminergic neurons possess auto receptors, which essentially act as an off switch when too much dopamine is being transmitted. This negative feedback loop works to stabilize dopaminergic transmission.
 
When a patient with early PD takes an oral dose of L-dopa, it is converted into dopamine in the central serotonergic neurons and the excess dopamine is buffered by retained dopaminergic neurons.
 
As PD advances, more significant destruction of these dopaminergic terminals means a loss in the capacity to buffer excess dopamine, which in turn can lead to dyskinesia.
 
I believe that there are particularly exciting results in preclinical and clinical studies exploiting this framework. For example, we have learned that there is a synergistic effect on dyskinesia reduction that occurs when agonists of 5-HT1A and 1B receptors are administered to animal models of PD. 
 
This presumably occurs because the serotonergic autoreceptors are being stimulated by the serotonin agonists. This may explain why previous studies using sarizotan, which is only a 5-HT1A agonist, did not show significant LID reduction. More recent clinical studies have taken advantage of this synergistic effect by giving eltoprazine, which is a dual 5-HT1A/1B agonist. Clinical trials with eltoprazine showed significant reduction in LID symptoms on two different clinical scales—the Clinical Dyskinesia Rating Scale and the Rush Dyskinesia Rating Scale.
 
You also discussed alpha-lipoic acid as a treatment option. How can this work to delay the onset of LID?
 
 Alpha-lipoic acid research revolves around the central finding that patients treated with L-dopa have been shown to have enhanced processes of oxidative stress occurring in their brains. 
 
There are a few possible reasons for this reaction. It might be that these patients have lower antioxidant levels or excessive oxidation of dopamine or disruptions in the mitochondrial transport chain. 
 
Other studies have found increased markers of oxidation and neuroinflammation present, which may suggest that monitoring these oxidative stress markers could be useful in some patients with PD who are receiving L-dopa. 
 
Some early studies found that alpha-lipoic acid could reduce reactive oxygen species and spare dopaminergic neurons in primate models of PD.
 
Recently we found more promising results when administering alpha-lipoic acid with L-dopa. Co-treatment had a dose-dependent anti-dyskinetic effect. 
 
When sampling of biomarkers and metabolites was done, the results corroborated the idea that alpha-lipoic acid might reduce oxidative stress and apoptosis to achieve neuroprotection.
 
It is also important to note this distinction with alpha-lipoic acid: among experimental Parkinson therapeutics it might be a disease-modifying agent. This is noteworthy when considering that most other therapies are simply just trying to alleviate symptoms of PD and dyskinesia.
 
More work still needs to be done in this area, including full-scale clinical studies to substantiate these claims in humans. But I do believe that the results to date are exciting. 
 
What other pharmacological approaches to LID look promising?
 
 There is another approach to LID that I believe to be promising, even though it is still a ways off from being clinically developed—it relates to beta-arrestin signaling.
 
Recent studies have elucidated that in addition to their roles as G-protein coupled receptors, dopamine receptors are also capable of signaling through a distinct beta-arrestin2-dependent pathway, in addition to the canonical G-protein pathway.
 
This is important because a lot of traditional dopamine agonists, including L-dopa, signal through dopamine D1/D2 receptors.
 
Other studies have also suggested that this G-protein independent pathway, the beta-arrestin pathway, along with traditional G-protein pathway, are important in regulating downstream responses at dopamine receptors. They play significant roles in converting dopamine signaling into motor function, which sheds new light on the known functions of beta-arrestins.
 
Some promising and exciting preclinical data has emerged, suggesting that beta-arrestin signaling is critical for locomotion in L-dopa and that when it is removed, locomotor responses to L-dopa are decreased and there is an increased propensity towards LID in these models.
 
Further validation for targeting beta-arrestin signaling at the dopamine receptors was provided in primate models of PD, where genetic overexpression of beta-arrestin reduced dyskinesias and rescued locomotion when L-dopa was given. 
 
I think we are at an exciting point in terms of the number of promising avenues that we have in devising potential strategies for treating LID. I think that innovations in this area have progressed significantly in recent years and I hope that at least a few of these experimental therapies might end up helping patients in the future.
 
*Martini ML, Neifert SN, Mocco J, et al. Recent Advances in the Development of Experimental Therapeutics for Levodopa-Induced Dyskinesia. J Mov Disord. 2019;12
 

How do we recognize and explain the necessity for a peak dose to patients with levodopa-induced dyskinesia (LID)?
 
The way I usually do it with my patients is I draw a graph. On the X axis I have time; on the Y axis I have levodopa levels. Then I show them on the graph a sinusoidal wave, displaying how, if they take their medication at 8 in the morning, the medication will grow in terms of concentration and then it will wear off.
 
With the sinusoidal wave I'm able to illustrate that at the peak a patient may have what we call "peak-dose dyskinesia." Typically for patients that's anywhere from 30 minutes to 45 minutes after they take their carbidopa/levodopa medication.
 
In terms of recognizing those symptoms, I usually spend some time with a patient describing what dyskinesia looks or feels like. There are certain cases where patients are unaware of their dyskinetic movements, when instead their caregiver, spouse, or partner are the ones actually recognizing the movements.
 
Typically, we talk about facial movements or lip/jaw movements and we can talk about upper extremity truncal writhing or hyperkinetic movements.
 
Sometimes, I'll have the patient come to the clinic having not taken their medication and then we evaluate them and have them take their medicine. About 30-45 minutes later we reevaluate the patient, which is when we can see the movements and have the patient look at themselves in the mirror to see what we're talking about, or at least explain movements to the caregiver.

 
Ultimately what we are trying to do is link the timing of medication and the timing of these side effects to help the patient and their family member understand the nature of what these symptoms are and when they're happening in relation to the medication that they're taking.
 
How can practitioners assess patients as their LID might become unpredictable?
 
I think the first step is to recognize that there are certain patients with Parkinson disease who are more likely to have adverse responses to levodopa. They're typically younger and they usually have other symptoms they are concerned about.
 
For example, it is very common for the patient to describe feeling stressed. I have had a number of patients tell me that when they're having anxiety or stress-related issues, such as at work or in their interpersonal relationships, that their dyskinesia might come on and progress a little bit more suddenly or unpredictably outside of that window when we typically expect it to peak.
 
Other triggers could be food. For instance, if a patient has changed their diet or changed the timing of their food intake, there may be issues related to gastric emptying or gastrointestinal symptoms that may influence the onset of these symptoms.

 
What we try to do is recognize the movements and then associate them with the environment or the timing behind the medication. When these things happen outside of the regular time when they're accustomed to getting them, we talk about these as unpredictable movements.
 
The other side effect is that patients can often have dystonia, or a forced muscle contraction. We are not only focused on the dyskinesia movement; dystonic movements are important as well.
 
Overall, I think practitioners can explain to patients the difference between these predictable and unpredictable movements. Additionally, we must help patients better recognize their symptoms and maybe the triggers for them, so that they may better manage them over time.
 
What are some aspects of LID that are most important to discuss with patients before a treatment?
 
The most important thing to talk about is the rationale for why a person would want to initiate levodopa or another medication.
 
Usually when a clinician is talking with a patient about pharmacotherapy they explain symptoms and how the individuals quality of life would improve if we treat them with levodopa.
 
We spend time explaining that the dose that's going to be required to get optimal control of their symptoms may differ in one person from another. And part of that dose selection is the fact that we're going to have to balance between not enough medication to too much medication.
 
So, I think the most important thing to discuss with patients is developing a strategy to come up with an individualized plan for medication management and explain to the patients the idea of on and off, explaining the idea of things that could interfere with medication, such as food or timing of medication use because of sleeping or changes to their day.
 
Basically, we are trying to give patients the framework for why we're dosing at certain times of the day regularly, why we're starting at a certain dose, and why we gradually increase the dose until we find resolution of their symptoms. We might explain why we may gradually reduce the dose if they are having symptoms like LID, and then why we may add other medications if they are experiencing LID. Also, we explain how and why we might not reduce the dose if a dose reduction would likely trigger worse symptoms.
 
Our aim is to give patients an outline of on/off factors that can affect drug availability and explain the long-term treatment goal, which is to optimize their motor symptoms to give them the best quality of life.

How do we recognize and explain the necessity for a peak dose to patients with levodopa-induced dyskinesia (LID)?
 
The way I usually do it with my patients is I draw a graph. On the X axis I have time; on the Y axis I have levodopa levels. Then I show them on the graph a sinusoidal wave, displaying how, if they take their medication at 8 in the morning, the medication will grow in terms of concentration and then it will wear off.
 
With the sinusoidal wave I'm able to illustrate that at the peak a patient may have what we call "peak-dose dyskinesia." Typically for patients that's anywhere from 30 minutes to 45 minutes after they take their carbidopa/levodopa medication.
 
In terms of recognizing those symptoms, I usually spend some time with a patient describing what dyskinesia looks or feels like. There are certain cases where patients are unaware of their dyskinetic movements, when instead their caregiver, spouse, or partner are the ones actually recognizing the movements.
 
Typically, we talk about facial movements or lip/jaw movements and we can talk about upper extremity truncal writhing or hyperkinetic movements.
 
Sometimes, I'll have the patient come to the clinic having not taken their medication and then we evaluate them and have them take their medicine. About 30-45 minutes later we reevaluate the patient, which is when we can see the movements and have the patient look at themselves in the mirror to see what we're talking about, or at least explain movements to the caregiver.

 
Ultimately what we are trying to do is link the timing of medication and the timing of these side effects to help the patient and their family member understand the nature of what these symptoms are and when they're happening in relation to the medication that they're taking.
 
How can practitioners assess patients as their LID might become unpredictable?
 
I think the first step is to recognize that there are certain patients with Parkinson disease who are more likely to have adverse responses to levodopa. They're typically younger and they usually have other symptoms they are concerned about.
 
For example, it is very common for the patient to describe feeling stressed. I have had a number of patients tell me that when they're having anxiety or stress-related issues, such as at work or in their interpersonal relationships, that their dyskinesia might come on and progress a little bit more suddenly or unpredictably outside of that window when we typically expect it to peak.
 
Other triggers could be food. For instance, if a patient has changed their diet or changed the timing of their food intake, there may be issues related to gastric emptying or gastrointestinal symptoms that may influence the onset of these symptoms.

 
What we try to do is recognize the movements and then associate them with the environment or the timing behind the medication. When these things happen outside of the regular time when they're accustomed to getting them, we talk about these as unpredictable movements.
 
The other side effect is that patients can often have dystonia, or a forced muscle contraction. We are not only focused on the dyskinesia movement; dystonic movements are important as well.
 
Overall, I think practitioners can explain to patients the difference between these predictable and unpredictable movements. Additionally, we must help patients better recognize their symptoms and maybe the triggers for them, so that they may better manage them over time.
 
What are some aspects of LID that are most important to discuss with patients before a treatment?
 
The most important thing to talk about is the rationale for why a person would want to initiate levodopa or another medication.
 
Usually when a clinician is talking with a patient about pharmacotherapy they explain symptoms and how the individuals quality of life would improve if we treat them with levodopa.
 
We spend time explaining that the dose that's going to be required to get optimal control of their symptoms may differ in one person from another. And part of that dose selection is the fact that we're going to have to balance between not enough medication to too much medication.
 
So, I think the most important thing to discuss with patients is developing a strategy to come up with an individualized plan for medication management and explain to the patients the idea of on and off, explaining the idea of things that could interfere with medication, such as food or timing of medication use because of sleeping or changes to their day.
 
Basically, we are trying to give patients the framework for why we're dosing at certain times of the day regularly, why we're starting at a certain dose, and why we gradually increase the dose until we find resolution of their symptoms. We might explain why we may gradually reduce the dose if they are having symptoms like LID, and then why we may add other medications if they are experiencing LID. Also, we explain how and why we might not reduce the dose if a dose reduction would likely trigger worse symptoms.
 
Our aim is to give patients an outline of on/off factors that can affect drug availability and explain the long-term treatment goal, which is to optimize their motor symptoms to give them the best quality of life.

How do we recognize and explain the necessity for a peak dose to patients with levodopa-induced dyskinesia (LID)?
 
The way I usually do it with my patients is I draw a graph. On the X axis I have time; on the Y axis I have levodopa levels. Then I show them on the graph a sinusoidal wave, displaying how, if they take their medication at 8 in the morning, the medication will grow in terms of concentration and then it will wear off.
 
With the sinusoidal wave I'm able to illustrate that at the peak a patient may have what we call "peak-dose dyskinesia." Typically for patients that's anywhere from 30 minutes to 45 minutes after they take their carbidopa/levodopa medication.
 
In terms of recognizing those symptoms, I usually spend some time with a patient describing what dyskinesia looks or feels like. There are certain cases where patients are unaware of their dyskinetic movements, when instead their caregiver, spouse, or partner are the ones actually recognizing the movements.
 
Typically, we talk about facial movements or lip/jaw movements and we can talk about upper extremity truncal writhing or hyperkinetic movements.
 
Sometimes, I'll have the patient come to the clinic having not taken their medication and then we evaluate them and have them take their medicine. About 30-45 minutes later we reevaluate the patient, which is when we can see the movements and have the patient look at themselves in the mirror to see what we're talking about, or at least explain movements to the caregiver.

 
Ultimately what we are trying to do is link the timing of medication and the timing of these side effects to help the patient and their family member understand the nature of what these symptoms are and when they're happening in relation to the medication that they're taking.
 
How can practitioners assess patients as their LID might become unpredictable?
 
I think the first step is to recognize that there are certain patients with Parkinson disease who are more likely to have adverse responses to levodopa. They're typically younger and they usually have other symptoms they are concerned about.
 
For example, it is very common for the patient to describe feeling stressed. I have had a number of patients tell me that when they're having anxiety or stress-related issues, such as at work or in their interpersonal relationships, that their dyskinesia might come on and progress a little bit more suddenly or unpredictably outside of that window when we typically expect it to peak.
 
Other triggers could be food. For instance, if a patient has changed their diet or changed the timing of their food intake, there may be issues related to gastric emptying or gastrointestinal symptoms that may influence the onset of these symptoms.

 
What we try to do is recognize the movements and then associate them with the environment or the timing behind the medication. When these things happen outside of the regular time when they're accustomed to getting them, we talk about these as unpredictable movements.
 
The other side effect is that patients can often have dystonia, or a forced muscle contraction. We are not only focused on the dyskinesia movement; dystonic movements are important as well.
 
Overall, I think practitioners can explain to patients the difference between these predictable and unpredictable movements. Additionally, we must help patients better recognize their symptoms and maybe the triggers for them, so that they may better manage them over time.
 
What are some aspects of LID that are most important to discuss with patients before a treatment?
 
The most important thing to talk about is the rationale for why a person would want to initiate levodopa or another medication.
 
Usually when a clinician is talking with a patient about pharmacotherapy they explain symptoms and how the individuals quality of life would improve if we treat them with levodopa.
 
We spend time explaining that the dose that's going to be required to get optimal control of their symptoms may differ in one person from another. And part of that dose selection is the fact that we're going to have to balance between not enough medication to too much medication.
 
So, I think the most important thing to discuss with patients is developing a strategy to come up with an individualized plan for medication management and explain to the patients the idea of on and off, explaining the idea of things that could interfere with medication, such as food or timing of medication use because of sleeping or changes to their day.
 
Basically, we are trying to give patients the framework for why we're dosing at certain times of the day regularly, why we're starting at a certain dose, and why we gradually increase the dose until we find resolution of their symptoms. We might explain why we may gradually reduce the dose if they are having symptoms like LID, and then why we may add other medications if they are experiencing LID. Also, we explain how and why we might not reduce the dose if a dose reduction would likely trigger worse symptoms.
 
Our aim is to give patients an outline of on/off factors that can affect drug availability and explain the long-term treatment goal, which is to optimize their motor symptoms to give them the best quality of life.

David Charles, MD, and Thomas Davis, MD, of the Vanderbilt University Department of Neurology, recently spoke with Neurology Reviews about the treatment pipeline and latest research in levodopa-induced dyskinesia in Parkinson's disease.

How is the treatment pipeline advancing for different types of levodopa-induced dyskinesia (LID)?
 
Dr. Thomas Davis: Dyskinesia has traditionally been hard to quantify, and we have been lacking any US Food and Drug Administration (FDA)-approved anti-dyskinesia drugs. The pipeline has historically been strongest for wearing-off because it is easier to measure on time than to quantify involuntary movements.

The Unified Dyskinesia Rating Scale (UDysRS), released in 2008 by the Movement Disorder Society, provided a standardized scale that allowed dyskinesia clinical trials to move forward. The UDysRS was used as the primary outcome for the extended release amantadine capsule study. This was important because it demonstrated the possibility of a successful clinical trial design to get a drug approved for dyskinesia, which will encourage others to test more potential new treatments.
 
What is the status of research on deep brain stimulation (DBS) for Parkinson's disease, and when might it be considered?
 
Dr. David Charles: This is one of the areas of research that we're focused on here at Vanderbilt. All 3 of the FDA-approved device manufacturers have been conducting research in technology refinement and improvements. These advances include not only patient programmers and physician programmers, but also new sensing capability and lead designs. Some of the manufacturers now have leads that allow the physician to steer the current in one direction or another, where traditionally the current has been delivered in a circumferential contact that's shaped like a cylinder, where the energy is transmitted 360 degrees from the lead. The new designs allow you to steer the current hopefully toward areas that provide more efficacy and away from areas that cause side effects. Even more exciting is the emerging sensing capability that may allow the development of stimulating technology that is responsive to fluctuating symptoms. There is keen research interest in understanding whether a device could detect a specific neuronal firing pattern and then respond with an individually tailored stimulation to improve symptoms as needed. Will the next generation of deep brain stimulating devices detect the pattern and deliver energy in a more targeted and precise way, responsive to what it's sensing from the patient's brain? I think that's an area of research that's really exciting.
 
In regard to when it might be considered: The ability to steer the current is already available in 2 of the 3 systems that are on the market today. Having current that is steerable in all 3 will be coming in the not too distant future. The available devices already have improved programming platforms for health care providers as well.
 
Our research at Vanderbilt is focused on DBS in early-stage Parkinson's disease. There is a paper published in Neurology that reports Class II evidencet hat DBS applied in early-stage Parkinson's disease slows the progression of tremor. This is exciting because none of the available treatments change the progression of disease—they're currently accepted as symptomatic therapies only. In this publication, we report that participants receiving DBS in the very earliest stages of Parkinson's disease it may slow the progression of rest tremor. We now have approval from the FDA to conduct a large-scale phase 3, multicenter, clinical trial of DBS in early-stage Parkinson's disease, with the primary endpoint focused on slowing progression of tremor, a cardinal feature of the disease. This upcoming trial is approved by the FDA as a pivotal trial, meaning that the findings could potentially be used to change the labeling of DBS devices. Our goal is to obtain Class I evidence of slowing the progression of tremor or other elements of the disease.
 
Dr. Thomas Davis: If you are a device manufacturer for DBS it is natural for you to aim to make better devices, better batteries, better programming, and better electrodes than your competitor. That's really where the industry-based research is right now. Clinicians are still determining which device is the best candidate, where the best target in the brain is, and when to use DBS.

When would a health care practitioner decide to try frequent smaller dosages or immediate-release formulations of dopaminergic drugs to control levodopa-induced dyskinesia (LID), compared with non-dopaminergic treatments that are available? What are some pros and cons of each approach?
 
Dr. David Charles: If you have a patient who's already on levodopa, it's not uncommon that—separate from the way we prescribe the medicine—the patients experiment with their medicine to some degree. At the very least, people occasionally forget to take a dose and they feel the effect of a missed dose. They may take an extra dose or an extra half dose, particularly if they feel that the last dose isn't working as well, or in the event they have some special occasion coming up. 
 
Over time, patients and physicians learn that sometimes smaller, more frequent dosing of levodopa can be a helpful strategy for certain individuals. One advantage is that it's the medication that the patient is already taking, and they're just simply breaking tablets. Many pharmacies will break tablets for patients so they can take some smaller doses more frequently. Obviously, there can be downsides to that, such as it becoming harder to remember to take more frequent doses.
 
Dr. Thomas Davis: I would agree that the biggest advantage of taking more frequent, smaller doses is that it's cheaper than adding an adjunct or moving to a more invasive therapy.  More frequent smaller doses of levodopa also generally has no side effects because if you're taking 2 carbidopa/levodopa 3 times a day and you're tolerating it, but you're having peak dose problems, you can then switch to 1.5 tablets 4 times a day. It involves more work and planning, but it's no more total medication than the patient is taking already, so this strategy usually does not have any unexpected side effects. It really boils down to how much work the patient wants to put in, how adherent they are to medication dosing, and whether they want to add another medication.
 
Most of the adjunctive medications to treat motor fluctuations are approved to improve on-time in Parkinson's disease patients with wearing off. These include the monoamine oxidase inhibitors, COMT inhibitors, and adenosine A2A antagonists. For treatment of dyskinesia, only the extended release capsule formulation of amantadine has FDA approval, although all formulations are approved for Parkinson's disease and are used clinically to dampen dyskinesia. How long to try these strategies before moving to one of the more advanced therapies, like DBS or jejunal infusion of levodopa, is not clear. It's great to have options, but it makes the decisions a lot harder.
 
Dr. David Charles: Dr. Davis raised the question of what medicine to choose, and what's your next choice in a patient who's having wearing-off dyskinesia or LID and so forth. There is an increasing number of options for those mid-stage patients. The pitfall is feeling that you have to try every available medication and combination before moving to a more advanced therapy.  The physician risks churning through the various combinations for so long that the benefit of an advanced therapy becomes shortened or lost altogether. 
 
Take epilepsy, for example. In operative candidates, surgery is often more beneficial when applied earlier. There's solid data to support that adding on multiple anti-epileptics medications is not always helpful. Continuing to add or change medications can actually diminish returns, particularly in a person who could receive benefit from surgery for epilepsy. 
 
I get the sense that the same may be true for dyskinesia. In clinical practice, we often receive DBS referrals when a patient's community-based physician has tried various medications and combination therapies until the point that the patient and the physician have become totally frustrated. By the time they are referred, the patient may benefit from DBS, but not nearly as well and as for long as they could have if they had received it earlier. We as physicians have to be mindful that while we have these increasing number of options—which is a good thing for both patients and physicians—that we don't continue to use them to the point that it takes away the option of more advanced therapies for appropriate candidates.
 
Metabotropic glutamate (mGlu) receptors have been receiving attention as potential therapeutic targets for LID. How do these compare with other receptors such as N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA)?
 
Dr. Thomas Davis: NMDA and AMPA are traditional ionotropic receptors, meaning that they are ligand gated, that they are almost exclusively excitatory, and that they generally have to do with the flow of potassium. 
 
mGlu receptors are protein coupled receptors. They have more elaborate action and may be either excitatory or inhibitory. Though mGlu, NMDA, and AMPA are completely different, they are all activated by glutamate. Pharmacologically utilizing the mGlu receptors is a relatively new and novel idea. Specifically, mGlu-5 receptors have received the most attention as potentially having an anti-parkinsonian effect and possibly dampening dyskinesia. The mGlu-5 receptors are an attractive target because they are concentrated in the striatum, as opposed to other glutamatergic receptors that are more diffusely located. It was felt that mGlu-5 modulators would be more specific and have less of the potential adverse effects of other glutamates. Most drugs that we think of affecting glutamate, like amantadine and memantine (used for Alzheimer's disease), have some NMDA antagonist effect, but this is relatively mild. 

David Charles, MD, and Thomas Davis, MD, of the Vanderbilt University Department of Neurology, recently spoke with Neurology Reviews about the treatment pipeline and latest research in levodopa-induced dyskinesia in Parkinson's disease.

How is the treatment pipeline advancing for different types of levodopa-induced dyskinesia (LID)?
 
Dr. Thomas Davis: Dyskinesia has traditionally been hard to quantify, and we have been lacking any US Food and Drug Administration (FDA)-approved anti-dyskinesia drugs. The pipeline has historically been strongest for wearing-off because it is easier to measure on time than to quantify involuntary movements.

The Unified Dyskinesia Rating Scale (UDysRS), released in 2008 by the Movement Disorder Society, provided a standardized scale that allowed dyskinesia clinical trials to move forward. The UDysRS was used as the primary outcome for the extended release amantadine capsule study. This was important because it demonstrated the possibility of a successful clinical trial design to get a drug approved for dyskinesia, which will encourage others to test more potential new treatments.
 
What is the status of research on deep brain stimulation (DBS) for Parkinson's disease, and when might it be considered?
 
Dr. David Charles: This is one of the areas of research that we're focused on here at Vanderbilt. All 3 of the FDA-approved device manufacturers have been conducting research in technology refinement and improvements. These advances include not only patient programmers and physician programmers, but also new sensing capability and lead designs. Some of the manufacturers now have leads that allow the physician to steer the current in one direction or another, where traditionally the current has been delivered in a circumferential contact that's shaped like a cylinder, where the energy is transmitted 360 degrees from the lead. The new designs allow you to steer the current hopefully toward areas that provide more efficacy and away from areas that cause side effects. Even more exciting is the emerging sensing capability that may allow the development of stimulating technology that is responsive to fluctuating symptoms. There is keen research interest in understanding whether a device could detect a specific neuronal firing pattern and then respond with an individually tailored stimulation to improve symptoms as needed. Will the next generation of deep brain stimulating devices detect the pattern and deliver energy in a more targeted and precise way, responsive to what it's sensing from the patient's brain? I think that's an area of research that's really exciting.
 
In regard to when it might be considered: The ability to steer the current is already available in 2 of the 3 systems that are on the market today. Having current that is steerable in all 3 will be coming in the not too distant future. The available devices already have improved programming platforms for health care providers as well.
 
Our research at Vanderbilt is focused on DBS in early-stage Parkinson's disease. There is a paper published in Neurology that reports Class II evidencet hat DBS applied in early-stage Parkinson's disease slows the progression of tremor. This is exciting because none of the available treatments change the progression of disease—they're currently accepted as symptomatic therapies only. In this publication, we report that participants receiving DBS in the very earliest stages of Parkinson's disease it may slow the progression of rest tremor. We now have approval from the FDA to conduct a large-scale phase 3, multicenter, clinical trial of DBS in early-stage Parkinson's disease, with the primary endpoint focused on slowing progression of tremor, a cardinal feature of the disease. This upcoming trial is approved by the FDA as a pivotal trial, meaning that the findings could potentially be used to change the labeling of DBS devices. Our goal is to obtain Class I evidence of slowing the progression of tremor or other elements of the disease.
 
Dr. Thomas Davis: If you are a device manufacturer for DBS it is natural for you to aim to make better devices, better batteries, better programming, and better electrodes than your competitor. That's really where the industry-based research is right now. Clinicians are still determining which device is the best candidate, where the best target in the brain is, and when to use DBS.

When would a health care practitioner decide to try frequent smaller dosages or immediate-release formulations of dopaminergic drugs to control levodopa-induced dyskinesia (LID), compared with non-dopaminergic treatments that are available? What are some pros and cons of each approach?
 
Dr. David Charles: If you have a patient who's already on levodopa, it's not uncommon that—separate from the way we prescribe the medicine—the patients experiment with their medicine to some degree. At the very least, people occasionally forget to take a dose and they feel the effect of a missed dose. They may take an extra dose or an extra half dose, particularly if they feel that the last dose isn't working as well, or in the event they have some special occasion coming up. 
 
Over time, patients and physicians learn that sometimes smaller, more frequent dosing of levodopa can be a helpful strategy for certain individuals. One advantage is that it's the medication that the patient is already taking, and they're just simply breaking tablets. Many pharmacies will break tablets for patients so they can take some smaller doses more frequently. Obviously, there can be downsides to that, such as it becoming harder to remember to take more frequent doses.
 
Dr. Thomas Davis: I would agree that the biggest advantage of taking more frequent, smaller doses is that it's cheaper than adding an adjunct or moving to a more invasive therapy.  More frequent smaller doses of levodopa also generally has no side effects because if you're taking 2 carbidopa/levodopa 3 times a day and you're tolerating it, but you're having peak dose problems, you can then switch to 1.5 tablets 4 times a day. It involves more work and planning, but it's no more total medication than the patient is taking already, so this strategy usually does not have any unexpected side effects. It really boils down to how much work the patient wants to put in, how adherent they are to medication dosing, and whether they want to add another medication.
 
Most of the adjunctive medications to treat motor fluctuations are approved to improve on-time in Parkinson's disease patients with wearing off. These include the monoamine oxidase inhibitors, COMT inhibitors, and adenosine A2A antagonists. For treatment of dyskinesia, only the extended release capsule formulation of amantadine has FDA approval, although all formulations are approved for Parkinson's disease and are used clinically to dampen dyskinesia. How long to try these strategies before moving to one of the more advanced therapies, like DBS or jejunal infusion of levodopa, is not clear. It's great to have options, but it makes the decisions a lot harder.
 
Dr. David Charles: Dr. Davis raised the question of what medicine to choose, and what's your next choice in a patient who's having wearing-off dyskinesia or LID and so forth. There is an increasing number of options for those mid-stage patients. The pitfall is feeling that you have to try every available medication and combination before moving to a more advanced therapy.  The physician risks churning through the various combinations for so long that the benefit of an advanced therapy becomes shortened or lost altogether. 
 
Take epilepsy, for example. In operative candidates, surgery is often more beneficial when applied earlier. There's solid data to support that adding on multiple anti-epileptics medications is not always helpful. Continuing to add or change medications can actually diminish returns, particularly in a person who could receive benefit from surgery for epilepsy. 
 
I get the sense that the same may be true for dyskinesia. In clinical practice, we often receive DBS referrals when a patient's community-based physician has tried various medications and combination therapies until the point that the patient and the physician have become totally frustrated. By the time they are referred, the patient may benefit from DBS, but not nearly as well and as for long as they could have if they had received it earlier. We as physicians have to be mindful that while we have these increasing number of options—which is a good thing for both patients and physicians—that we don't continue to use them to the point that it takes away the option of more advanced therapies for appropriate candidates.
 
Metabotropic glutamate (mGlu) receptors have been receiving attention as potential therapeutic targets for LID. How do these compare with other receptors such as N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA)?
 
Dr. Thomas Davis: NMDA and AMPA are traditional ionotropic receptors, meaning that they are ligand gated, that they are almost exclusively excitatory, and that they generally have to do with the flow of potassium. 
 
mGlu receptors are protein coupled receptors. They have more elaborate action and may be either excitatory or inhibitory. Though mGlu, NMDA, and AMPA are completely different, they are all activated by glutamate. Pharmacologically utilizing the mGlu receptors is a relatively new and novel idea. Specifically, mGlu-5 receptors have received the most attention as potentially having an anti-parkinsonian effect and possibly dampening dyskinesia. The mGlu-5 receptors are an attractive target because they are concentrated in the striatum, as opposed to other glutamatergic receptors that are more diffusely located. It was felt that mGlu-5 modulators would be more specific and have less of the potential adverse effects of other glutamates. Most drugs that we think of affecting glutamate, like amantadine and memantine (used for Alzheimer's disease), have some NMDA antagonist effect, but this is relatively mild. 

David Charles, MD, and Thomas Davis, MD, of the Vanderbilt University Department of Neurology, recently spoke with Neurology Reviews about the treatment pipeline and latest research in levodopa-induced dyskinesia in Parkinson's disease.

How is the treatment pipeline advancing for different types of levodopa-induced dyskinesia (LID)?
 
Dr. Thomas Davis: Dyskinesia has traditionally been hard to quantify, and we have been lacking any US Food and Drug Administration (FDA)-approved anti-dyskinesia drugs. The pipeline has historically been strongest for wearing-off because it is easier to measure on time than to quantify involuntary movements.

The Unified Dyskinesia Rating Scale (UDysRS), released in 2008 by the Movement Disorder Society, provided a standardized scale that allowed dyskinesia clinical trials to move forward. The UDysRS was used as the primary outcome for the extended release amantadine capsule study. This was important because it demonstrated the possibility of a successful clinical trial design to get a drug approved for dyskinesia, which will encourage others to test more potential new treatments.
 
What is the status of research on deep brain stimulation (DBS) for Parkinson's disease, and when might it be considered?
 
Dr. David Charles: This is one of the areas of research that we're focused on here at Vanderbilt. All 3 of the FDA-approved device manufacturers have been conducting research in technology refinement and improvements. These advances include not only patient programmers and physician programmers, but also new sensing capability and lead designs. Some of the manufacturers now have leads that allow the physician to steer the current in one direction or another, where traditionally the current has been delivered in a circumferential contact that's shaped like a cylinder, where the energy is transmitted 360 degrees from the lead. The new designs allow you to steer the current hopefully toward areas that provide more efficacy and away from areas that cause side effects. Even more exciting is the emerging sensing capability that may allow the development of stimulating technology that is responsive to fluctuating symptoms. There is keen research interest in understanding whether a device could detect a specific neuronal firing pattern and then respond with an individually tailored stimulation to improve symptoms as needed. Will the next generation of deep brain stimulating devices detect the pattern and deliver energy in a more targeted and precise way, responsive to what it's sensing from the patient's brain? I think that's an area of research that's really exciting.
 
In regard to when it might be considered: The ability to steer the current is already available in 2 of the 3 systems that are on the market today. Having current that is steerable in all 3 will be coming in the not too distant future. The available devices already have improved programming platforms for health care providers as well.
 
Our research at Vanderbilt is focused on DBS in early-stage Parkinson's disease. There is a paper published in Neurology that reports Class II evidencet hat DBS applied in early-stage Parkinson's disease slows the progression of tremor. This is exciting because none of the available treatments change the progression of disease—they're currently accepted as symptomatic therapies only. In this publication, we report that participants receiving DBS in the very earliest stages of Parkinson's disease it may slow the progression of rest tremor. We now have approval from the FDA to conduct a large-scale phase 3, multicenter, clinical trial of DBS in early-stage Parkinson's disease, with the primary endpoint focused on slowing progression of tremor, a cardinal feature of the disease. This upcoming trial is approved by the FDA as a pivotal trial, meaning that the findings could potentially be used to change the labeling of DBS devices. Our goal is to obtain Class I evidence of slowing the progression of tremor or other elements of the disease.
 
Dr. Thomas Davis: If you are a device manufacturer for DBS it is natural for you to aim to make better devices, better batteries, better programming, and better electrodes than your competitor. That's really where the industry-based research is right now. Clinicians are still determining which device is the best candidate, where the best target in the brain is, and when to use DBS.

When would a health care practitioner decide to try frequent smaller dosages or immediate-release formulations of dopaminergic drugs to control levodopa-induced dyskinesia (LID), compared with non-dopaminergic treatments that are available? What are some pros and cons of each approach?
 
Dr. David Charles: If you have a patient who's already on levodopa, it's not uncommon that—separate from the way we prescribe the medicine—the patients experiment with their medicine to some degree. At the very least, people occasionally forget to take a dose and they feel the effect of a missed dose. They may take an extra dose or an extra half dose, particularly if they feel that the last dose isn't working as well, or in the event they have some special occasion coming up. 
 
Over time, patients and physicians learn that sometimes smaller, more frequent dosing of levodopa can be a helpful strategy for certain individuals. One advantage is that it's the medication that the patient is already taking, and they're just simply breaking tablets. Many pharmacies will break tablets for patients so they can take some smaller doses more frequently. Obviously, there can be downsides to that, such as it becoming harder to remember to take more frequent doses.
 
Dr. Thomas Davis: I would agree that the biggest advantage of taking more frequent, smaller doses is that it's cheaper than adding an adjunct or moving to a more invasive therapy.  More frequent smaller doses of levodopa also generally has no side effects because if you're taking 2 carbidopa/levodopa 3 times a day and you're tolerating it, but you're having peak dose problems, you can then switch to 1.5 tablets 4 times a day. It involves more work and planning, but it's no more total medication than the patient is taking already, so this strategy usually does not have any unexpected side effects. It really boils down to how much work the patient wants to put in, how adherent they are to medication dosing, and whether they want to add another medication.
 
Most of the adjunctive medications to treat motor fluctuations are approved to improve on-time in Parkinson's disease patients with wearing off. These include the monoamine oxidase inhibitors, COMT inhibitors, and adenosine A2A antagonists. For treatment of dyskinesia, only the extended release capsule formulation of amantadine has FDA approval, although all formulations are approved for Parkinson's disease and are used clinically to dampen dyskinesia. How long to try these strategies before moving to one of the more advanced therapies, like DBS or jejunal infusion of levodopa, is not clear. It's great to have options, but it makes the decisions a lot harder.
 
Dr. David Charles: Dr. Davis raised the question of what medicine to choose, and what's your next choice in a patient who's having wearing-off dyskinesia or LID and so forth. There is an increasing number of options for those mid-stage patients. The pitfall is feeling that you have to try every available medication and combination before moving to a more advanced therapy.  The physician risks churning through the various combinations for so long that the benefit of an advanced therapy becomes shortened or lost altogether. 
 
Take epilepsy, for example. In operative candidates, surgery is often more beneficial when applied earlier. There's solid data to support that adding on multiple anti-epileptics medications is not always helpful. Continuing to add or change medications can actually diminish returns, particularly in a person who could receive benefit from surgery for epilepsy. 
 
I get the sense that the same may be true for dyskinesia. In clinical practice, we often receive DBS referrals when a patient's community-based physician has tried various medications and combination therapies until the point that the patient and the physician have become totally frustrated. By the time they are referred, the patient may benefit from DBS, but not nearly as well and as for long as they could have if they had received it earlier. We as physicians have to be mindful that while we have these increasing number of options—which is a good thing for both patients and physicians—that we don't continue to use them to the point that it takes away the option of more advanced therapies for appropriate candidates.
 
Metabotropic glutamate (mGlu) receptors have been receiving attention as potential therapeutic targets for LID. How do these compare with other receptors such as N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA)?
 
Dr. Thomas Davis: NMDA and AMPA are traditional ionotropic receptors, meaning that they are ligand gated, that they are almost exclusively excitatory, and that they generally have to do with the flow of potassium. 
 
mGlu receptors are protein coupled receptors. They have more elaborate action and may be either excitatory or inhibitory. Though mGlu, NMDA, and AMPA are completely different, they are all activated by glutamate. Pharmacologically utilizing the mGlu receptors is a relatively new and novel idea. Specifically, mGlu-5 receptors have received the most attention as potentially having an anti-parkinsonian effect and possibly dampening dyskinesia. The mGlu-5 receptors are an attractive target because they are concentrated in the striatum, as opposed to other glutamatergic receptors that are more diffusely located. It was felt that mGlu-5 modulators would be more specific and have less of the potential adverse effects of other glutamates. Most drugs that we think of affecting glutamate, like amantadine and memantine (used for Alzheimer's disease), have some NMDA antagonist effect, but this is relatively mild.