Warnings and precautions to be aware of prior to taking carbidopa include the following:
Carbidopa should always be combined with levodopa products (like Sinemet®, Sinemet® CR, Parcopa®, or Stalevo®), since carbidopa itself has no activity against Parkinson's disease.
Because carbidopa (combined with levodopa) can activate a malignant melanoma, it should not be used by anyone with a suspicious undiagnosed skin lesion or a history of melanoma.
Carbidopa (with levodopa) can cause involuntary muscle movements called dyskinesias. Although usually not dangerous, dyskinesias are usually quite disturbing and intolerable. If you develop a dyskinesia while taking carbidopa, your healthcare provider may need to decrease your carbidopa dosage (or you may need to stop taking carbidopa altogether).
Carbidopa (with levodopa) can cause or worsen many mental illnesses, due to its effects on dopamine (a brain chemical). Let your healthcare provider know if you have a history of such problems.
If you have heart problems, lung problems, ulcers, or kidney or liver disease, check with your healthcare provider before taking carbidopa. In some cases, carbidopa (with levodopa) may not be the best choice for you.
Stopping carbidopa (with levodopa) too quickly can cause a dangerous condition known as neuroleptic malignant syndrome (NMS). Do not stop taking carbidopa without your healthcare provider's approval and supervision. Let your healthcare provider know if you develop any signs of NMS, such as:
People with glaucoma may not be able to take carbidopa (with levodopa) safely. Carbidopa is not recommended at all for people with narrow-angle glaucoma. People with adequately treated wide-angle glaucoma may take carbidopa, although careful monitoring of the condition may be necessary.
The medication (when combined with levodopa) may cause you to fall asleep during the day, sometimes without warning. This can be especially dangerous if you are driving a car or operating heavy machinery. In addition, this can happen long after you start taking carbidopa. Ask your healthcare provider if you should stop driving a car or operating heavy machinery while taking carbidopa.
Carbidopa (with levodopa) can cause dark (red, brown, or black) saliva, sweat, or urine. Although this is not dangerous, it can be quite bothersome.
Carbidopa is considered a pregnancy Category C medication. This means that it may not be safe for use during pregnancy, although the full risks are not known (see Lodosyn and Pregnancy).
It is not known whether carbidopa passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Lodosyn and Breastfeeding).