Prescription Medications

Although there are general guidelines that doctors use to choose a treatment regimen, each person with PD must be individually evaluated to determine which drug or combination of drugs is best for them. For some, a “first choice” drug might be one of the levodopa preparations, and for others, an initial prescription may be given for one of the agonists, an MAO inhibitor or an anticholinergic.

The choice of drug treatment depends on many variables including symptom presentation, other concurrent health issues (and the medications being used to treat them) and a person’s age. And while the suggested starting dosages (as indicated by the package insert) are listed here, remember that they too can vary greatly depending on a person’s needs and metabolism.

Below, we summarize types (“classes”) of medications available to treat Parkinson’s on the market, along with each specific medication.  If you would like to print an overview of what appears here, please click here to download our two-page fact sheet.  For more detailed information, please scroll below.

• Carbidopa/Levodopa therapy
• Dopamine Agonists
• Anticholinergics
• MAO-B Inhibitors
• COMT Inhibitors
• Other medications

Carbidopa/Levodopa (Sinemet®)The most potent medication for Parkinson’s is levodopa. Its development in the late 1960s represents one of the most important breakthroughs in the history of medicine. Plain levodopa produces nausea and vomiting. It is now combined with carbidopa to prevent this side effect. The well-known combined carbidopa/levodopa formulation is called Sinemet®

There are many different preparations and strengths of carbidopa/levodopa, including longacting forms and a formulation that dissolves in the mouth without water, called Parcopa®. There is also a combined formulation that includes the COMT inhibitor entacapone, called Stalevo®.

It is important that people with Parkinson’s are aware which levodopa preparation they are taking because there are so many different pill sizes, strengths and manufacturers. Be careful when renewing prescriptions at the pharmacy because the accidental substitute of a different formulation may lead to an overdosage or underdosage.

Carbidopa/levodopa remains the most effective drug for treating Parkinson’s. The addition of carbidopa prevents levodopa from being converted into dopamine in the bloodstream, allowing more of it to get to the brain. Therefore, a smaller dose of levodopa is needed to treat symptoms.

Some people with PD have been reluctant to take it, believing it to be a last resort. But most neurologists agree that delaying treatment too long is unwise, and may put a person with PD at risk for falling. The decision about when to start carbidopa/levodopa is different for every person with Parkinson’s, and requires consideration of potential benefits, risks and the availability of alternatives.

Unfortunately, with increased dosing and prolonged use of levodopa, patients experience other side effects including dyskinesias (spontaneous, involuntary movements) and "on-off" periods when the medication will suddenly and unpredictably start or stop working. Check with a doctor before taking any of the following to avoid possible interactions: antacids, anti-seizure drugs, anti-hypertensives, anti-depressants and high protein food. The same drugs that interact with carbidopa/levodopa and entacapone interact with Stalevo®.

Dopamine agonists are drugs that stimulate the parts of the human brain influenced by dopamine. In effect, the brain is tricked into thinking it is receiving the dopamine it needs. In general, dopamine agonists are not as potent as carbidopa/levodopa, and therefore are less likely to cause dyskinesias. Dopamine agonists can be taken alone or in combination with medications containing levodopa. The two most commonly prescribed oral pill agonists in the US are pramipexole (Mirapex) and ropinirole (Requip). A third, rotigotine transdermal system (Neupro®), was recently re-approved after several years of being off the market. Bromocriptine (Parlodel® ) is available, but is less commonly used.

As a class, dopamine agonists may cause nausea, hallucinations, sedation (including sudden sleepiness, called sleep attacks) and lightheadedness due to low blood pressure, so it is important to start at a low dose, increase gradually and be alert for side effects. In some people (in a recent study up to 14 percent), these medications have also been linked with compulsive behaviors, such as gambling and shopping.

One dopamine agonist, apomorphine (Apokyn), is a powerful and fast-acting injectable medication that promptly relieves symptoms of PD within minutes, but only provides 30 to 60 minutes of benefit. With training provided by the Parkinson’s specialist, people with PD, spouses and family members can be taught to administer the agent, using a pre-filled syringe system. Its main advantage is its rapid effect. It is used for people who experience sudden wearing-off spells when their Parkinson’s medication abruptly stops working, leaving them unexpectedly immobile. Apomorphine may cause severe nausea, and so people using this agent must take an antiemetic agent. In addition, apomorphine can provoke dyskinesias and other side effects associated with dopamine drugs.

Consult a doctor before taking any of the following to avoid possible interactions: alcohol, anti-psychotics, medications that lower blood pressure, Navane® (thiothixene), Taractan® (chlorprothixene), Haldol® (haloperidol), Reglan® (metoclopramide), phenothiazines, thiozanthenes, cimetidine, phenothiazines, butyrophenones, Cipro® and benzodiazepines.

Anticholinergics Anticholinergics can be helpful for tremor and may ease dystonia associated with wearing-off or peak-dose effect. They have little effect on other symptoms of Parkinson’s. The drugs in this class include trihexyphenidyl (Artane®), benztropine mesylate (Cogentin®) and procyclidine (no longer available in the US), among others. They do not act directly on the dopaminergic system. Instead, they decrease the activity of acetylcholine, a neurotransmitter that regulates movement. Potential adverse effects include blurred vision, dry mouth, constipation and urinary retention.

Older individuals are susceptible to confusion and hallucinations on anticholinergics, so these agents should be avoided in individuals over the age of 70.  Adverse effects of these drugs include blurred vision, dry mouth and urinary retention.

Check with a doctor before using anticholinergics with anti-histamines, Haldol®, Thorazine®, Symmetrel®, Clozaril® and alcohol.

MAO-B inhibitors — selegiline (also called deprenyl, with trade names Eldepryl®and Zelapar®) and rasagiline (Azilect®) — block an enzyme in the brain that breaks down levodopa. These drugs have a modest effect in suppressing the symptoms of Parkinson’s. They have been shown to delay the need for Sinemet when prescribed in the earliest stage of Parkinson’s, and have been approved for use in later stages of PD to boost the effects of Sinemet. Eldepryl® may interact with anti-depressants, narcotic pain killers and decongestants. Check with a doctor before taking any new medications.

COMT inhibitors such as entacapone (Comtan®) and tolcapone (Tasmar®) represent the newest class of Parkinson's medications. These agents have no direct effect on PD symptoms, but instead are used to prolong the effect of levodopa by blocking its metabolism. COMT inhibitors are used primarily to help with the problem of wearing-off, in which the effect of levodopa becomes short-lived. People who take Tasmar must have regular liver function blood tests. Entacapone is not only a COMT inhibitor, but is also one of the main ingredients in Stalevo.

Other medications such as amantadine (Symmetrel) is a mild agent that is used in early Parkinson’s disease to help tremor. In recent years, amantadine has also been found useful in reducing dyskinesias that occur with dopamine medication. Amantadine is a well-tolerated drug, but its potential side effects include dry mouth, constipation, bladder
problems, ankle swelling and skin rash. Rivastigmine (Exelon) is the only medication approved by the US Food and Drug Administration for the treatment of dementia in PD.

* Please note that the side effects listed in the tables that accompany each class of medication are the most commonly experienced. Not all individuals will experience such side effects. For many people who do experience side effects, they can often be effectively limited or eliminated with careful adjustments to dosage or the timing of the individual doses. If any side effects are experienced, speak to the treating physician immediately. For a complete description of each drug and its possible side effects, please request a “package insert” from your pharmacist for each drug being used. It is recommended that all prescriptions be filled at the same pharmacy to avoid interactions between medications. Interactions can be dangerous and even life-threatening, so make sure the pharmacist knows of all medications and supplements being taken – including over-the-counter medications and supplements.

Next: Over-the-Counter Medications