Parkinsons Disease Home > Comtan Warnings and Precautions

Let your healthcare provider know if you have lung problems, gallbladder disease, or any allergies before starting Comtan. Warnings and precautions also include watching out for potential drug interactions and possibly avoiding the medication if you have liver or kidney disease. Make sure to talk to your healthcare provider about the precautions and warnings with Comtan to help ensure a safe treatment process.

Comtan: What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking Comtan® (entacapone) if you have:
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
Make sure to tell your healthcare provider about any medications you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Comtan Warnings and Precautions

Warnings and precautions to be aware of prior to taking Comtan include the following:
  • Comtan should always be used in combination with carbidopa-levodopa products (such as Sinemet®, Sinemet® CR, or Parcopa®). Comtan has no activity against Parkinson's disease when used alone.
  • Stopping the drug too quickly can cause a dangerous condition known as neuroleptic malignant syndrome (NMS). Do not stop taking Comtan without your healthcare provider's approval and supervision. Let your healthcare provider know if you develop any signs of NMS, such as:
    • A high fever
    • Irregular pulse or blood pressure
    • A fast heart rate (tachycardia)
    • Sweating
    • Stiff muscles
    • Confusion
    • Irregular heart rhythms (arrhythmias).
  • Comtan often causes diarrhea. Sometimes, it can be severe enough to require hospitalization. This diarrhea can occur at any time, not just when starting the medication.


  • Intense, unusual urges have been reported in people taking Parkinson's disease medications. Examples include an intense desire to gamble or to engage in risky sexual behavior. Let your healthcare provider know right away if you experience any of these urges.
  • People with Parkinson's disease have an increased risk for melanoma (a type of skin cancer). At this time, it is not clear if this is caused by Parkinson's disease medications or other factors. It is a good idea to have regular skin checks to monitor for this problem. 


  • The medication can cause low blood pressure (hypotension). Be sure to let your healthcare provider know if you develop signs of low blood pressure, such as lightheadedness, dizziness, or fainting.
  • Comtan can cause hallucinations (seeing, hearing, or feeling things that are not there). Let your healthcare provider know if you develop hallucinations while taking the drug.
  • The medication can cause involuntary muscle movements called dyskinesias. Although not usually dangerous, dyskinesias can be disturbing and intolerable. If you develop a dyskinesia while taking Comtan, your healthcare provider may need to decrease your Comtan dosage, or you may need to stop taking the drug altogether.
  • In animal studies, large doses of Comtan increased the risk of kidney problems in rats. It is not known if the drug causes kidney problems in humans too.
  • If you have bile or gallbladder problems, lung problems, ulcers, or kidney or liver disease, check with your healthcare provider before taking Comtan. In some cases, this medication may not be the best choice for you.
  • The medication 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 Comtan. Ask your healthcare provider if you should stop driving a car or operating heavy machinery while taking it.
  • Comtan can cause urine discoloration. This is not dangerous and is not a sign of other problems.
  • Comtan can potentially interact with several medications (see Comtan Drug Interactions).
  • Comtan is considered a pregnancy Category C medication. This means it may not be safe for use during pregnancy, although the full risks are not known (see Comtan and Pregnancy).
  • It is not known whether Comtan 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 Comtan and Breastfeeding).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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