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.