Dopamine Agonists for Parkinson's Disease

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Dopamine Agonists for Parkinson's Disease


Generic NameBrand Name

How It Works

Dopamine agonists directly stimulate the receptors in nerves in the brain that normally would be stimulated by dopamine. Unlike levodopa, a dopamine agonist is not changed (converted) into dopamine when it enters the body, but it behaves like dopamine.

Why It Is Used

Dopamine agonists may be used in the early stages of Parkinson's disease to reduce symptoms. This approach is often effective in people who have been newly diagnosed with the disease (especially those younger than 60), because it can delay the need for levodopa and thus postpone the motor fluctuations that may occur with long-term levodopa therapy.

A dopamine agonist may be added to treatment with levodopa in the later stages of Parkinson's disease when:

  • Levodopa no longer is able to adequately control symptoms on its own, and increasing the dose to provide adequate control of symptoms would cause excessive side effects.
  • The person who is taking levodopa is experiencing severe motor fluctuations.

Apomorphine is an injectable, rapid-acting dopamine agonist. It is injected into the skin during occasional episodes of immobility when muscles become "stuck" or "frozen," and you are unable to rise from a chair or perform daily activities. Treatment with apomorphine is referred to as "rescue" therapy, because it is used during periods when levodopa or other dopamine agonists are not effective or have worn off.

How Well It Works

When used alone in early Parkinson's disease, dopamine agonists may reduce symptoms of the disease, especially those that affect motor function, such as stiffness and slowness. Although they are not as effective as levodopa in controlling symptoms, they have the benefit of postponing the need for levodopa therapy. This in turn may help delay the onset of levodopa-related motor fluctuations.

When taken in combination with levodopa, dopamine agonists may:1

  • Reduce the amount of levodopa needed to control symptoms, thereby reducing some side effects of levodopa.
  • Improve motor function during both "on" and "off" periods.
  • Reduce involuntary movements (dyskinesias) associated with long-term levodopa therapy, if the dose of levodopa can be reduced. But if you have been taking levodopa for a long time (many years), dopamine agonists may also cause abnormal muscle movements.
  • Prolong the effect of levodopa and reduce motor fluctuations that occur as a result of the wearing-off effect of levodopa, when the effects of a dose do not last as long as they did before.

Because apomorphine is rapid-acting, it is usually effective within 10 minutes from the time of injection. It works for approximately 60 to 90 minutes.

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call 911 or other emergency services right away if you have:

  • Trouble breathing.
  • Swelling of your face, lips, tongue, or throat.


Call your doctor right away if you have:

  • Hives.
  • Chest pain, discomfort, or pressure.
  • Chills or cold sweats.
  • Confusion, hallucinations, or mood or mental changes.
  • Dizziness, lightheadedness, or fainting.
  • Uncontrollable movements, such as twitching or repetitive movements of the tongue, lips, face, arms, or legs.

Common side effects of this medicine include:

  • Skin problems where you inject the medicine, such as bleeding, blistering, rash, redness, swelling, or scarring.
  • Blurred vision.
  • Drowsiness, sleepiness, and yawning.
  • Runny nose.

Other dopamine agonists

Call your doctor right away if you have:

  • Hives.
  • Dizziness, lightheadedness, or fainting.
  • Confusion or hallucinations.
  • Nausea.
  • Sudden attacks of sleepiness where you fall asleep without warning, even in the middle of the day.
  • Uncontrollable movements, such as twitching or repetitive movements of the tongue, lips, face, arms, or legs.
  • Unusual tiredness or weakness.

Common side effects of this medicine include:

  • Constipation.
  • Dry mouth.
  • Headache.
  • Heartburn or indigestion.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

The decision about whether it is better to use levodopa or a dopamine agonist as the first treatment in Parkinson's disease is different for each person. Levodopa controls symptoms better than dopamine agonists in most people. And levodopa has fewer side effects than dopamine agonists. But concern about levodopa-related motor fluctuations is leading some doctors to use dopamine agonists as initial therapy in people with newly diagnosed Parkinson's disease in order to delay treatment with levodopa. The American Academy of Neurology now recommends this approach for most people who have the disease.

In theory, the purpose behind delaying treatment with levodopa, especially in younger people with Parkinson's, is to delay the motor fluctuations that eventually occur with levodopa therapy. But in the long term, the same amount of people have motor fluctuations no matter what medicine is used first.2 If a dopamine agonist is used as initial therapy, levodopa may be added when the dopamine agonist is no longer able to control symptoms adequately on its own.

Apomorphine causes severe nausea and vomiting and must be taken with anti-nausea medicine. Do not drink alcohol when you are using apomorphine.

Dopamine agonists may cause impulse-control disorders in some people. Impulse-control disorders include uncontrollable or problem gambling, sexual behavior, and shopping. Binge eating is another example.

Dopamine agonists are more likely than levodopa to cause impulse-control disorders. But your risk is even higher if you take both a dopamine agonist and levodopa. If you are concerned about taking these medicines because of this risk, talk with your doctor.

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.



  1. Clarke CE, Moore AP (2007). Parkinson's disease, search date November 2006. BMJ Clinical Evidence. Available online:
  2. Katzenschlager R, et al. (2008). Fourteen-year final report of the randomized PDRG-UK trial comparing three initial treatments in PD. Neurology, 71(7): 474–480.


ByHealthwise Staff
Primary Medical ReviewerAnne C. Poinier, MD - Internal Medicine
Specialist Medical ReviewerG. Frederick Wooten, MD - Neurology
Last RevisedJanuary 25, 2013

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