Carbidopa is used with another medicine called levodopa to treat symptoms of Parkinson's disease, such as stiffness or tremors.

Carbidopa and levodopa are also used to treat Parkinson-like symptoms caused by taking certain medicines or by exposure to poisonous gases or minerals such as carbon monoxide or manganese.

Carbidopa is only used in combination with levodopa and has no effect when used alone.

Carbidopa may also be used for purposes not listed in this medication guide.

Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, or tranylcypromine.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

If you already take levodopa but have never taken carbidopa, start taking both medicines at least 12 hours after you last took levodopa by itself.

Take both carbidopa and levodopa together at regular intervals, to keep steady amounts in your body at all times.

You may need frequent medical tests.

Your symptoms may not improve for several weeks. Call your doctor if your symptoms do not improve or if the effects of this medicine wear off quickly between doses.

You may have withdrawal symptoms if you stop using carbidopa suddenly. Ask your doctor before stopping the medicine.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using carbidopa.

Store at room temperature away from moisture and heat.

Usual Adult Dose for Parkinsonian Tremor:

Patients on carbidopa-levodopa therapy requiring additional carbidopa:
Initial dose: 25 mg orally with the first dose of carbidopa-levodopa each day
Maintenance dose: Additional doses of 12.5 mg or 25 mg may be given with each dose of carbidopa-levodopa
Maximum dose: 200 mg orally per day

Patients requiring individual titration of carbidopa and levodopa:
Initial dose: 25 mg orally 3 to 4 times a day, given at the same time as levodopa
Maximum dose: 200 mg orally per day

Comments:
-Most patients respond to a 1:10 proportion of carbidopa and levodopa, provided the daily dosage of carbidopa is 70 mg or more a day; for patients taking carbidopa-levodopa, the amount of carbidopa in carbidopa-levodopa should be considered when calculating the maximum daily carbidopa dose.
-In patients already on levodopa, allow 12 hours between the last dose of levodopa and the initiation of therapy with carbidopa and levodopa.

Uses: With carbidopa-levodopa or with levodopa in the treatment of symptoms of idiopathic Parkinson's disease (paralysis agitans), postencephalitic parkinsonism, and symptomatic parkinsonism

You should not use carbidopa if you are allergic to it, or if you have:

• narrow-angle glaucoma.

Do not use carbidopa if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, tranylcypromine, and others.

Tell your doctor if you have ever had:

• nausea and vomiting while taking levodopa;

• heart disease, high blood pressure;

• liver or kidney disease;

• a stomach or intestinal ulcer;

• glaucoma; or

• depression, mental illness, or psychosis.

People with Parkinson's disease may have a higher risk of skin cancer (melanoma). Ask your doctor about skin symptoms to watch for.

It is not known if carbidopa will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

You should not breastfeed while using carbidopa.

Not approved for use by anyone younger than 18 years old.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Get your prescription refilled before you run out of medicine completely.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Avoid driving or hazardous activity until you know how carbidopa will affect you. Your reactions could be impaired. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Avoid taking iron supplements or eating a diet high in protein. These things can make it harder for your body to digest and absorb carbidopa and levodopa. Talk with your doctor or dietitian about the best foods to eat or avoid.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

The following side effects may occur when carbidopa is taken with levodopa.

Carbidopa may cause serious side effects. Call your doctor at once if you have:

• severe drowsiness;

• uncontrolled muscle movements in your face (chewing, lip smacking, frowning, tongue movement, blinking or eye movement);

• worsening of tremors (uncontrolled shaking);

• severe nausea, vomiting, or diarrhea;

• confusion, hallucinations, unusual changes in mood or behavior;

• depression or suicidal thoughts;

• seizure (convulsions); or

• severe nervous system reaction--very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, feeling like you might pass out.

Some people taking carbidopa with levodopa have fallen asleep during normal daytime activities such as working, talking, eating, or driving. Tell your doctor if you have any problems with daytime sleepiness or drowsiness.

You may have increased sexual urges, unusual urges to gamble, or other intense urges while taking carbidopa. Talk with your doctor if this occurs.

You may notice that your sweat, urine, or saliva appears dark in color, such as red, brown, or black. This is not a harmful side effect, but it may cause staining of your clothes or bed sheets.

Common side effects of carbidopa may include:

• nausea, upset stomach;

• headache, dizziness;

• sleep problems (insomnia), dreaming more than usual;

• dry mouth, burning feeling in your tongue;

• weight changes; or

• abnormal liver function tests.

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.

Using carbidopa with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Other drugs may affect carbidopa, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.