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What is carbidopa?

Carbidopa is used with levodopa to treat Parkinson’s disease. Parkinson’s disease is believed to be related to low levels of a chemical called dopamine (DOE pa meen) in the brain. Levodopa (Dopar, Larodopa) is turned into dopamine in the body. Carbidopa is used with levodopa to prevent the breakdown (metabolism) of levodopa before it can reach the brain and take effect. Carbidopa is only effective if it is taken with levodopa. It has no effect if it is used alone.

Carbidopa is used with levodopa to treat the stiffness, tremors, spasms, and poor muscle control of Parkinson’s disease. These medications are also used to treat the same muscular conditions when they are caused by drugs such as chlorpromazine (Thorazine), fluphenazine (Prolixin), perphenazine (Trilafon), and others.

Carbidopa may also be used for purposes other than those listed in this medication guide.

Precautions

Instructions

Side Effects

Interactions

Precautions

Do not take this medication without first talking to your doctor if you have

• taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), tranylcypromine (Parnate), or phenelzine (Nardil) in the past 2 weeks;
• narrow-angle glaucoma (angle closure glaucoma); or
• malignant melanoma (a type of skin cancer).

Before taking this medication, tell your doctor if you have

• heart disease, high blood pressure, arteriosclerosis, hardening of the arteries, a previous heart attack, or an irregular heartbeat;
• respiratory disease, including asthma and chronic obstructive pulmonary disease (COPD);
• liver disease;
• kidney disease;
• an endocrine (hormonal) disease;
• a stomach or intestinal ulcer;
• wide-angle glaucoma; or
• depression or any other psychiatric disorder.

You may need a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.

It is not known whether carbidopa will be harmful to an unborn baby. Do not take carbidopa without first talking to your doctor if you are pregnant or could become pregnant during treatment.

It is also not known whether carbidopa will be harmful to a nursing infant. Do not take carbidopa without first talking to your doctor if you are breast-feeding a baby.

Use caution when driving, operating machinery, or performing other hazardous activities. Carbidopa may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

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Instructions

Seek emergency medical attention if an overdose is suspected.

Symptoms of a carbidopa overdose include muscle spasms or weakness, spasms of the eyelid, nausea, vomiting, diarrhea, an irregular heartbeat, confusion, agitation, hallucinations, and unconsciousness.

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and only take the next regularly scheduled dose. Do not take a double dose of this medication.

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Side Effects

Carbidopa alone is not associated with side effects. The following side effects are generally associated with carbidopa and levodopa therapy.

If you experience any of the following serious side effects, stop taking carbidopa and levodopa and seek emergency medical attention or contact your doctor immediately:

• an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
• uncontrolled movements of a part of the body;
• seizures;
• persistent nausea, vomiting, or diarrhea;
• an irregular heartbeat or fluttering in your chest;
• unusual changes in mood or behavior; or
• depression or suicidal thoughts.

Other, less serious side effects may be more likely to occur. Continue to take carbidopa and levodopa and talk to your doctor if you experience

• mild nausea, vomiting, or decreased appetite;
• constipation, dry mouth, or blurred vision;
• hand tremor;
• muscle twitches;
• dizziness or drowsiness;
• insomnia, confusion, or nightmares;
• agitation or anxiety;
• darkening of urine or sweat; or
• fatigue.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. You may report side effects to FDA at 1-800-FDA-1088.

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Interactions

Do not take carbidopa and levodopa if you have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), phenelzine (Nardil), or tranylcypromine (Parnate) in the past 14 days.

Antacids may increase the effectiveness of carbidopa and levodopa and lead to side effects. Ask your doctor about the use of antacids.

Before taking carbidopa, tell your doctor if you are taking any of the following medicines:

• a medicine to treat high blood pressure (hypertension);
• a medicine used to treat seizures, such as phenytoin (Dilantin), ethotoin (Peganone), or mephenytoin (Mesantoin);
• papaverine (Pavabid, Cerespan, others);
• pyridoxine or vitamin B6;
• an antidepressant such as amitriptyline (Elavil), doxepin (Sinequan), nortriptyline (Pamelor), desipramine (Norpramin), and amoxapine (Asendin); or
• a medicine used to treat a psychiatric condition (or nausea and vomiting), such as chlorpromazine (Thorazine), fluphenazine (Prolixin), mesoridazine (Serentil), thioridazine (Mellaril), trifluoperazine (Stelazine), and haloperidol (Haldol).

You may not be able to take carbidopa, or you may require a dosage adjustment or special monitoring if you are taking any of the medicines listed above.

Levodopa may interfere with urine tests for sugar and ketones. If you have diabetes and notice changes in urine test results, talk to your doctor before making any changes in your diabetes medication.

Drugs other than those listed here may also interact with carbidopa. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including vitamins, minerals, and herbal products.

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