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.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.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; orif 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.

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Carbidopa Side EffectsGet 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); orsevere 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:nausea, upset stomach;headache, dizziness;sleep problems (insomnia), dreaming more than usual;dry mouth, burning feeling in your tongue;weight changes; orabnormal 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.

Source: http://www.everydayhealth.com