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Drugs reference index «Entacapone»


Pronunciation: (en-TAK-a-pone)Class: Antiparkinson agent

Trade Names:Comtan- Tablets 200 mg


The exact mechanism of action is unknown. Inhibits catechol-O-methyltransferase (COMT), thus blocking the degradation of catechols, including dopamine and levodopa. This may lead to more sustained levels of dopamine and consequently a more prolonged antiparkinson effect.



Rapidly absorbed. T max is approximately 1 h. C max is approximately 1.2 mcg/mL (single 200 mg dose). Absolute bioavailability is 35%.


Vd is 20 L (IV). 98% is protein bound, mainly to albumin.


Almost completely metabolized; inactive metabolites formed by isomerization and glucuronidation.


Approximately 10% is excreted in the urine (0.2% as unchanged drug) and 90% in feces.

Special Populations

Renal Function Impairment

No important effects of renal function on the pharmacokinetics of entacapone have been demonstrated.

Hepatic Function Impairment

AUC and C max are approximately 2-fold higher in those with a history of alcoholism and hepatic impairment.


Pharmacokinetics of entacapone are independent of age.


No studies have been conducted.

Indications and Usage

As an adjunct to levodopa/carbidopa for the treatment of idiopathic Parkinson disease in patients who experience signs and symptoms of end-of-dose “wearing-off.”


Standard considerations.

Dosage and Administration


PO 200 mg concomitantly with each levodopa/carbidopa dose; max, 8 times/day.

General Advice

  • May be taken with or without food.


Store at 59° to 86°F.

Drug Interactions

Ampicillin, chloramphenicol, cholestyramine, erythromycin, probenecid, rifampin

May interfere with biliary excretion or metabolism of entacapone. Use with caution.

Apomorphine, dobutamine, dopamine, epinephrine, isoproterenol, methyldopa, norepinephrine

Excessive changes in BP and increased heart rate, possibly arrhythmias, may occur. Use with caution. Closely monitor the clinical response of the patient.


Because MAO and COMT are the 2 major enzyme systems involved in catecholamine metabolism, it is theoretically possible that the combination of entacapone and a nonselective MAOI (eg, phenelzine, tranylcypromine) could result in inhibition of the majority of the pathways responsible for normal catecholamine metabolism. Therefore, usually do not treat patients concomitantly with entacapone and a nonselective MAOI. However, entacapone may be coadministered with a selective MAOI-B (eg, selegiline).

Laboratory Test Interactions

None well documented.

Adverse Reactions


Orthostatic hypotension (4%).


Dyskinesia (25%); hyperkinesia (10%); hypokinesia (9%); dizziness (8%); fatigue (6%); hallucinations (4%); anxiety, asthenia, somnolence (2%); agitation (1%).


Taste perversion (1%).


Nausea (14%); diarrhea (10%); abdominal pain (8%); constipation (6%); vomiting (4%); dry mouth (3%); dyspepsia, flatulence (2%); gastritis, GI disorders (1%).


Urine discoloration (10%).


Purpura (2%).


Dyspnea (3%).


Back pain (4%); sweating increased (2%); bacterial infection (1%).



Monitor patients closely if entacapone is discontinued. Monitor patients for melanoma frequently and on a regular basis.


Category C .




Safety and efficacy not established.

Hepatic Function

Use with caution.


May occur as early as the first week or as late as many months after initiating entacapone.


Exercise caution when discontinuing treatment. Withdrawal of entacapone should proceed slowly.


Entacapone may cause and/or exacerbate preexisting dyskinesia.

Fibrotic complications

Cases of retroperitoneal fibrosis, pulmonary infiltrates, pleural effusion, and pleural thickening have been reported.


May occur.

Hyperpyrexia and confusion

Rhabdomyolysis and a symptom complex resembling NMS reported in association with therapy. Exercise caution.


May increase the incidence of orthostatic hypotension associated with dopaminergic therapy.


Risk of melanoma is higher in patients with Parkinson disease compared with the general population; however, it has not been determined if this is caused by the disease or the treatment.



Abdominal pain, loose stools.

Patient Information

  • Inform patient that entacapone is not a cure for Parkinson disease, but should help reduce the symptoms and decrease the need for higher doses of their other medications.
  • Instruct patient to take entacapone only as prescribed.
  • Advise patient that hallucinations can occur.
  • Advise patient that postural (orthostatic) hypotension with or without symptoms such as dizziness, nausea, sweating, and syncope may develop. Hypotension may occur more frequently during initial therapy.
  • Caution patient against rising rapidly, especially after prolonged periods of sitting or lying down.
  • Caution patient about possible additive sedative effects when taking other CNS depressants in combination with entacapone.
  • Caution patient not to drive a car, operate other complex machinery, or engage in any hazardous activity until tolerance is determined.
  • Inform patient that nausea or hypotension may occur, especially at the initiation of treatment.
  • Advise patients of the possibility of an increase in dyskinesia.
  • Advise patients of the possibility of experiencing intense urges while taking one or more of the medications generally used to treat Parkinson disease. Instruct patients to inform their health care provider if they experience new or increased gambling urges, sexual urges, or other intense urges while taking entacapone.
  • Inform patient that treatment with entacapone may cause a change in urine color to a brownish orange in approximately 10% of people, but that it will not cause harm should it occur.
  • Advise patient to notify health care provider if she is pregnant, planning to become pregnant, or breast-feeding.

Copyright © 2009 Wolters Kluwer Health.

  • Entacapone Detailed Consumer Information (PDR)
  • Entacapone MedFacts Consumer Leaflet (Wolters Kluwer)
  • entacapone Concise Consumer Information (Cerner Multum)
  • entacapone Advanced Consumer (Micromedex) - Includes Dosage Information
  • Comtan Prescribing Information (FDA)

See Also...

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