There are several medications available that can help manage the symptoms of Parkinson’s disease (PD). While there is no known cure for PD or any known treatments that can slow the progression of the disease, current research seeks to find ways to stop the progression. Treatment is highly individualized to meet the needs of the unique patient, as no two people with PD are alike. PD shows up differently across people, and treatment for PD is focused on relieving or controlling the symptoms of PD for as long as possible, minimizing side effects from treatment, and improving quality of life.1,2
There are several different classes of drugs used to treat the symptoms of PD, including:
- Dopamine therapy, notably carbidopa-levodopa therapy
- Dopamine receptor agonists
- MAO-B (monoamine oxidase-B) inhibitors
- COMT (catechol-O-methyltransferase) inhibitors
- And other medications1,2
It is important for people with PD to see a movement disorders specialist who is trained in the use of these drugs for PD. Movement disorders specialists understand the interactions of these drugs and how some medications may make symptoms worse.
The motor symptoms of Parkinson’s—resting tremor, bradykinesia (gradual loss and slowing down of spontaneous movement), rigidity, and postural instability (impaired balance)—are caused by a lack of the neurotransmitter dopamine in the brain. Dopamine is the chemical messenger that is responsible for smooth, purposeful movement. The main drug treatments used for PD help increase the dopamine levels in the brain, and by doing so, they relieve the symptoms of PD. The combination of levodopa and carbidopa is the most effective treatment available for the management of motor symptoms of Parkinson’s disease (PD).
Dopamine receptor agonists
Dopamine receptor agonists are not as effective on the motor symptoms of PD as carbidopa-levodopa therapy, but they may have fewer side effects. Dopamine receptor agonists mimic dopamine in the brain, and neurons in the brain use the dopamine agonists instead of dopamine. This can provide relief from symptoms of PD, particularly the motor symptoms such as tremor, rigidity, impaired balance, and loss of spontaneous movement.3
Anticholinergics block the action of acetylcholine, another neurotransmitter involved in messages from the brain to the muscles. Anticholinergics are frequently used in combination with other treatments for PD.4,5
MAO is an enzyme found throughout the cells in the body. In the brain, MAO-B plays an important role in the breakdown of neurotransmitters (chemical messengers) like dopamine. MAO inhibitors block the action of the enzyme. Adding an MAO-B inhibitor to levodopa therapy slows the breakdown of levodopa and dopamine in the brain, and may boost the effect of levodopa.3,6
COMT (catechol-O-methyltransferase) is an enzyme that metabolizes or degrades neurotransmitters such as dopamine. COMT inhibitors block the action of the COMT enzyme. Adding a COMT inhibitor to levodopa therapy slows the breakdown of levodopa and dopamine, and may boost the effect of levodopa by making more of it available in the brain.7,8
Other medications that may be used in the treatment of PD include medications which treat specific symptoms, including dementia, hallucinations, delusions, depression, tremor, or orthostatic hypotension (a falling of blood pressure that occurs upon changing positions or standing).3 Not all antipsychotic medications are considered safe for people with PD but there are several that can be used to limit worsening of PD symptoms and treat symptoms of hallucination and delusion.