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Carbidopa

Generic Name: carbidopa (kar bi DOE pa)
Brand Name: Lodosyn

Medically reviewed on March 31, 2017.

What is carbidopa?

Carbidopa is used with another medicine called levodopa to treat the symptoms of Parkinson's disease (stiffness, tremors, spasms, poor muscle control). Symptoms of Parkinson's disease may be caused by low levels of a chemical called dopamine (DOE pa meen) in the brain.

Levodopa is converted to dopamine in the brain. Carbidopa helps prevent the breakdown of levodopa before it can reach the brain and take effect.

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

Carbidopa is also used with levodopa to treat muscle symptoms similar to Parkinson's disease that are caused by certain drugs such as chlorpromazine (Thorazine), fluphenazine (Prolixin), perphenazine (Trilafon), and others.

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

Important Information

You should not use carbidopa if you have narrow-angle glaucoma.

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, rasagiline, selegiline, or tranylcypromine.

Before taking this medicine

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

  • narrow-angle glaucoma.

Do not use carbidopa with levodopa 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, rasagiline, selegiline, tranylcypromine, and others.

To make sure carbidopa is safe for you, tell your doctor if you have:

  • a history of depression, mental illness, or psychosis;

  • a history of suicidal thoughts or actions; or

  • if you also take blood pressure medication.

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

It is not known whether carbidopa passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

Carbidopa is not approved for use by anyone younger than 18 years old.

How should I take carbidopa?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Take both carbidopa and levodopa at the same time.

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

Use carbidopa with levodopa regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

While using this medicine, you may need frequent blood tests. Your heart, kidney function, and liver function may also need to be checked.

It may take up to several weeks of using carbidopa with levodopa before your symptoms improve. For best results, keep using the medication as directed. Talk with your doctor if your symptoms do not improve after a few weeks of treatment. Also tell your doctor if the effects of this medication seem to wear off quickly in between doses.

Do not stop using carbidopa suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.

This medicine can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using carbidopa with levodopa.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

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

What should I avoid while taking carbidopa?

Avoid taking iron supplements or eating a diet that is high in protein (protein sources include meat, eggs, and cheese). These things can make it harder for your body to digest and absorb carbidopa and levodopa. Talk with your doctor or nutrition counselor about the best foods to eat while you are taking this medication.

This medicine may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Carbidopa side effects

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.

Call your doctor at once if you have:

  • 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 this medicine. 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 may include:

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.

See also: Side effects (in more detail)

Carbidopa dosing information

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 three to four times a day, given at the same time as levodopa
Maximum dose: 200 mg orally per day

Comments:
-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

What other drugs will affect carbidopa?

Other drugs may interact with carbidopa, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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