The use of medications for Parkinson’s disease can boost the amount of a chemical called dopamine in the brain. This neurotransmitter is affected in a number of ways depending on the mechanism of the medication prescribed.
- Levodopa (gets converted in the brain into dopamine). This is the mainstay of treatment and is most effective but also most likely to cause motor complications. Carbidopa-levodopa can cause nausea, lightheadedness upon standing, hallucinations, psychosis, intense urges, and dyskinesia. These side effects can often be alleviated with dose adjustments.
- Sinemet is the brand name for carbidopa-levodopa and is available in both immediate-release (IR) and controlled-release (CR or ER) formulations. However, the controlled-release formulation is not as predictable in absorption, compared to the IR formulation and has not been proven to reduce “off” time. Sinemet is taken 3 times per day to begin with and as the disease progresses the frequency is increased to 5 or 6 times per day.
- RytaryTM is the brand name for a new formulation of carbidopa-levodopa and is a new type of drug delivery with microcapsules within a capsule, resulting in a truly controlled release and a duration of action about an hour longer than immediate-release carbidopa-levodopa. Rytary capsules can be gently opened and sprinkled on applesauce, making it a good alternate for patients who cannot swallow medications.
- Dopamine agonists work on the same brain cell receptors as dopamine. Imagine the dopamine receptor as the lock and dopamine as the key. Dopamine agonists are like a different key for the same lock. Mirapex is the brand name for pramipexole; Requip is the brand name for ropinirole; and the Neupro patch is the only transdermal Parkinson’s medication. This can be useful for patients who are unable to swallow. Dopamine agonists have a lower risk of motor complications than levodopa but a higher risk of sleepiness, impulse control disorders (compulsive behaviors) and swelling in the legs.
- MAO-B inhibitors reduce metabolism of dopamine, thereby boosting the amount of dopamine in the brain. Azilect (rasagiline) is a once-a-day medication; Eldepryl (selegiline) is taken twice a day. Effectiveness for motor symptoms is milder. Side effects include high blood pressure, insomnia and abdominal pain. They can be used by themselves or with levodopa.
- COMT inhibitors reduce metabolism of levodopa, thereby boosting the amount of dopamine in the brain. They only work when taken with levodopa. Brand names include Comtan (entacapone) and Stalevo (a combination of carbidopa, levodopa and entacapone). They improve the duration of action of levodopa but can make dyskinesias (involuntary movement) worse and may cause confusion or diarrhea.
- Amantadine is an antiviral medication (also used for the flu) which modulates the release of dopamine and can help for tremor or dyskinesias, but can cause swelling in the legs, depression or anxiety symptoms, and blurry vision.
- Artane (trihexyphenidyl) blocks the acetylcholine system which is in imbalance with the dopamine system, and improving the flow of dopamine. This medication is primarily useful for patients with tremor and for the small subset of PD patients who have dystonia, but can cause confusion, anxiety, depression, dry mouth, constipation, dry eyes.
- Treatment for non-motor symptoms associated with PD is also available.