How It Works
Levodopa is a medicine that the brain
Carbidopa is a medicine (called
a decarboxylase inhibitor) that, when taken with levodopa, helps prevent the
levodopa from converting to dopamine outside the brain. The combination of
carbidopa and levodopa has several benefits:
- It allows more levodopa to get to the brain and
thus increases the supply of dopamine in the brain.
- It decreases
side effects caused by increased dopamine levels outside the brain by reducing
the supply of "free" dopamine outside the brain. (Increased dopamine levels
outside the brain can result in side effects such as nausea, vomiting, and low
- It enhances the effect of levodopa, so that less
levodopa is needed to control symptoms.
Why It Is Used
Levodopa is a medicine used to
control symptoms of
Parkinson's disease and may be used at all stages of
How Well It Works
Levodopa is the most effective
medicine for relieving symptoms of Parkinson's disease. It helps reduce tremor,
stiffness, and slowness and helps improve muscle control, balance, and walking.
It does not affect
freezing, dementia, or problems with involuntary
(autonomic) functions, such as constipation, urinary problems, impotence, or
Levodopa does not slow the disease
process, but it improves muscle movement and delays severe disability. The use
of levodopa allows people with Parkinson's disease to stay independent and
able to function for longer periods of time. But the majority of people
taking levodopa develop complications caused by long-term levodopa therapy
within 5 to 10 years. Movement problems (motor fluctuations)
are the most common and troublesome complication.
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:
Call your doctor if you have:
- Agitation or anxiety.
- Confusion, hallucinations, abnormal thinking, or holding false beliefs that cannot be changed by fact.
- Clumsiness or unsteadiness.
Dizziness, lightheadedness, or fainting.
- Difficulty swallowing or excessive mouth-watering.
- Nausea or vomiting.
- Uncontrollable movements, such as twitching or repetitive movements of the tongue, lips, face, arms, or legs.
- Unusual tiredness or weakness.
- Worse tremor.
Common side effects of this medicine include:
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.
Levodopa 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.
Levodopa is less likely than dopamine agonists 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.
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.
Minagar A, et al. (2003). Parkinson's disease. In RW
Evans, ed., Saunders Manual of Neurologic Practice, pp.
205–209. Philadelphia: Saunders.
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.
Primary Medical Reviewer
||Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer
||G. Frederick Wooten, MD - Neurology
Current as of
||March 12, 2014