Project Description

Many Medications Are Available for Parkinson’s Disease

Learn more about the different classes of medications through the American Parkinson Disease Association.

First discovered in the early 1960s, Levodopa (L-dopa) has been considered the most effective drug in treating symptoms of PD.[i] Simply put, it is the gold standard of PD drug treatment. L-dopa is a precursor to dopamine, which is deficient in patients with PD. It has been shown to slow down the sequence of disability, and has been linked with decreased mortality.[ii] Carbidopa was combined with L-dopa (LD) to create a more efficacious combination Sinemet, which reduces one of the side effects: nausea. It helps prevent the breakdown of LD. Other lingering side effects of LD include dizziness, orthostatic hypertension, anxiety, confusion, somnolence, and the big one, irreversible dyskinesias, or uncontrollable, involuntary movements.[iii]

Dyskinesias usually occur in most patients after about two years of therapy.[iv] Once it happens, it becomes difficult to treat, and creates a major disability. Due to concerns about this complication, some neurologists delay using LD on patients, instead opting for it as a second-line drug.[v] Results from clinical trials has shown that some de novo drugs such as dopamine agonists (DA), such as pramipexole or ropinirole can potentially reduce the risks of developing dyskinesias, seen with LD. [vi]Yet they have equally proven how effective LD is, in most cases, most patients who were initially placed on a DA, usually eventually need LD supplementation.[vii]

Due to widespread perception about dyskinesias caused by LD, in clinical practice, many physicians sometimes hold back on LD, even when DAs are not as effective alone. DAs also have additional side effects discussed below.

Adjunct Medications

In addition to DAs, other medications have been created for use in PD.[viii] These are Catechol-O-methyl transferase (COMT) inhibitors, Monoamine Oxidase B Inhibitors (MAO-B inhibitors), amantadine, and anticholinergic inhibitors.[ix]

Dopamine Agonists (DA)

Dopamine agonists behave like dopamine. They include pramipexole, ropinirole, rotigotine, and apomorphine. DAs are given alone, or along with LD. While DAs reduce the risk of developing dyskinesias, they also increase the risk of having other side effects.[x] This is the main reason why some doctors are not as eager to administer it instead of LD. Pramipexole and ropinirole are taken orally, while rotigotine is given as a patch, and apromorphine is injected. DAs has a number of notable side effects as earlier stated. They cause excessive drowsiness, and in some instances can result in some behavioral side effects, including gambling, shopping, binge eating, and increased sexual behaviors. Once the DA dosage is decreased or the drug stopped, these changes resolve.

COMT inhibitors

These medications help lengthen the time period for LD to be effective.[xi] They are taken with LD, and not alone. They usually come into play when DAs prove ineffective, or are not tolerated. They are Entacapone (Comtan®) and Tolcapone (Tasmar®).

Monoamine Oxidase B Inhibitors (MAO-B inhibitors)

These medications such as selegiline work by inhibiting the MAO-B enzyme, which breaks down dopamine.[xii] This increases the action of dopamine in the brain. While some studies indicated that it may help slow the progression of PD, no full evidence exists.[xiii]

Amantadine

This medication can be given alone, or along with LD and a DA. It helps in decreasing symptoms of fatigue and tremor usually seen in the early stages of PD.[xiv]

Effect of DBS on Medications

According to research studies, at least one-third of patients saw a decrease in dopaminergic medications by 50 percent, up to 3 years after a DBS surgery.[xv] In addition to improving quality of life, and decreasing the number of times patients need to take their medications, it also helps significantly with cost.

References

[i] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[ii] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[iii] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[iv] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[v] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[vi] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[vii] Hinz, M., Stein, A., & Cole, T. (2014). Parkinson’s disease: Carbidopa, nausea, and dyskinesia. Clinical Pharmacology: Advances and Applications, 189. doi:10.2147/cpaa.s72234

[viii] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[ix] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[x] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[xi] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[xii] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[xiii] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[xiv] Parkinson’s Disease Clinic and Research Center. (2014). Retrieved February 12, 2019, from http://pdcenter.neurology.ucsf.edu/patients-guide/parkinson’s-disease-medications

[xv] Guduru, Z., Schramke, C., Baser, S., & Leichliter T. (2016). Medication Reduction After DBS Placement in Parkinson’s Disease (P6.383) Neurology Apr 2016, 86 (16 Supplement) P6.383;

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