Comtan Side Effects

Generic name: entacapone

Medically reviewed by Drugs.com. Last updated on May 15, 2023.

Note: This document contains side effect information about entacapone. Some dosage forms listed on this page may not apply to the brand name Comtan.

Applies to entacapone: oral tablet.

Serious side effects of Comtan

Along with its needed effects, entacapone (the active ingredient contained in Comtan) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking entacapone:

More common

Absence of or decrease in body movements
hyperactivity
increase in body movements
seeing, hearing, or feeling things that are not there
twisting
twitching
uncontrolled repetitive movements of the tongue, lips, face, arms, or legs

Less common

Cough or hoarseness
fever or chills
lower back or side pain
painful or difficult urination

Rare

Confusion
muscle cramps
pain
shortness of breath
stiffness
unusual tiredness or weakness

Other side effects of Comtan

Some side effects of entacapone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Abdominal or stomach pain
constipation
diarrhea
dizziness
nausea

Less common

Acid or sour stomach
anxiety
belching
bruising
burning feeling in the chest or stomach
difficult or labored breathing
dry mouth
heartburn
indigestion
irritability
loss of strength or energy
muscle pain or weakness
passing gas
restlessness
sleepiness or unusual drowsiness
small, red spots on the skin
stomach discomfort, upset, or tenderness
sweating increased
tightness in the chest
tremor
trouble sleeping
unusual or unpleasant (after) taste
unusual weak feeling

For Healthcare Professionals

Applies to entacapone: oral tablet.

Nervous system

There were no cases of neuroleptic malignant syndrome during clinical trials. Since market introduction, there have been isolated cases, especially following abrupt reduction or discontinuation of this drug and other concomitant dopaminergic drugs.^[Ref]

Very common (10% or more): Dyskinesia (up to 27%), hyperkinesia (10%)

Common (1% to 10%): Hypokinesia, dizziness, somnolence, taste perversion, aggravated parkinsonism, dystonia, headache, tremor

Frequency not reported: Falling asleep during activities of daily living

Postmarketing reports: Neuroleptic malignant syndrome^[Ref]

Gastrointestinal

Very common (10% or more): Nausea (up to 14%), diarrhea (up to 11%)

Common (1% to 10%): Abdominal pain, constipation, vomiting, dry mouth, dyspepsia, flatulence, gastritis, gastrointestinal disorders

Very rare (less than 0.01%): Anorexia

Postmarketing reports: Colitis^[Ref]

In clinical trials, diarrhea occurred in approximately 10% of patients. It was generally mild to moderate, but in 1.3% of people it was severe. Upon discontinuation, diarrhea generally resolved. There have been postmarketing reports of drug-induced microscopic colitis, primarily lymphocytic colitis.^[Ref]

Genitourinary

Very common (10% or more): Urine discoloration (10%)^[Ref]

General

The most commonly reported adverse reactions included dyskinesia, urine discoloration, diarrhea, nausea, hyperkinesia, abdominal pain, vomiting, and dry mouth.^[Ref]

Respiratory

Common (1% to 10%): Dyspnea

Frequency not reported: Pulmonary fibrosis^[Ref]

Dermatologic

Common (1% to 10%): Increased sweating

Rare (less than 0.1%): Erythematous, maculopapular rash

Very rare (less than 0.01%): Urticaria

Frequency not reported: Skin hair, beard, and nail discolorations^[Ref]

Musculoskeletal

Isolated cases of rhabdomyolysis have occurred in patients treated with this drug. The complicated nature of these cases makes it difficult to determine the role this drug may have had. Rhabdomyolysis has been reported secondary to severe dyskinesias or neuroleptic malignant syndrome (NMS) in patients with Parkinson's disease.^[Ref]

Common (1% to 10%): Back pain, falls, leg cramps

Postmarketing reports: Rhabdomyolysis^[Ref]

Psychiatric

Common (1% to 10%): Anxiety, insomnia, hallucinations, confusion, paranoia

Uncommon (0.1% to 1%): Agitation

Frequency not reported: Impulse control disorders including pathological gambling, increased libido, hypersexuality, compulsive spending or buying, binge eating and compulsive eating^[Ref]

Hematologic

Common (1% to 10%): Purpura, decreased hemoglobin^[Ref]

A clinically significant decrease in hemoglobin has been observed in 1.8% of patients. The underlying mechanism may involve decreased absorption of iron from the gastrointestinal tract.^[Ref]

Other

Common (1% to 10%): Fatigue, asthenia, pain, vertigo^[Ref]

Cardiovascular

The incidence of myocardial infarction and other ischemic heart disease events was 0.43% and 1.54%, respectively, in an analysis of 13 double-blind studies involving 2082 patients.^[Ref]

Common (1% to 10%): Ischemic heart disease events other than myocardial infarction (e.g., angina pectoris, postural hypotension

Uncommon (0.1% to 1%): Myocardial infarction^[Ref]