Version July 2025
Parkinson disease: Oral: 200 mg with each dose of levodopa/carbidopa, up to a maximum of 8 times daily (maximum daily dose: 1600 mg daily).
Note: To optimize therapy, the dosage of levodopa may need to be reduced or the dosing interval may need to be extended. Patients taking levodopa ≥800 mg daily or who had moderate-to-severe dyskinesias prior to therapy required an average decrease of 25% in the daily levodopa dose.
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling; however, renal function was not found to significantly affect the pharmacokinetics of entacapone.
U.S. labeling: There are no dosage adjustments provided in the manufacturer's labeling. Treat with caution and monitor carefully; AUC and Cmax may possibly be doubled.
Canadian labeling: Use is contraindicated.
Refer to adult dosing.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Gastrointestinal: Nausea (14%)
Neuromuscular & skeletal: Dyskinesia (25%)
1% to 10%:
Cardiovascular: Syncope (1%)
Central nervous system: Dizziness (8%), fatigue (6%), anxiety (2%), drowsiness (2%), agitation (1%), hallucination (≤1%)
Dermatologic: Diaphoresis (increased; 2%)
Gastrointestinal: Diarrhea (10%), abdominal pain (8%), constipation (6%), vomiting (4%), xerostomia (3%), dyspepsia (2%), flatulence (2%), dysgeusia (1%), gastritis (1%), gastrointestinal disease (1%)
Genitourinary: Urine discoloration (brown-orange; 10%)
Hematologic & oncologic: Purpura (2%)
Infection: Bacterial infection (1%)
Neuromuscular & skeletal: Hyperkinesia (10%), hypokinesia (9%), back pain (2% to 4%), weakness (2%)
Respiratory: Dyspnea (3%)
<1%, postmarketing, and/or case reports: Behavioral changes (including psychotic-like behavior), hepatitis (mainly cholestatic features), impulse control disorder (eg, pathological gambling, hypersexuality, spending money), mental status changes, neurological signs and symptoms (hyperpyrexia and confusion [resembling neuroleptic malignant syndrome]), orthostatic hypotension, pulmonary fibrosis, retroperitoneal fibrosis, rhabdomyolysis, sudden onset of sleep
Hypersensitivity to entacapone or any component of the formulation
Canadian labeling: Additional contraindications (not in U.S. labeling): Clinical or laboratory evidence of uncompensated cardiovascular, endocrine, hematologic, pulmonary (including bronchial asthma), or renal disease; history of neuroleptic malignant syndrome (NMS) and/or nontraumatic rhabdomyolysis; hepatic impairment; narrow-angle glaucoma; pheochromocytoma; in the presence of a suspicious, undiagnosed skin lesion or history of melanoma; concomitant use with a nonselective monoamine oxidase (MAO) inhibitor (eg, tranylcypromine, phenelzine) or concomitant use with both a selective MAO-A and selective MAO-B inhibitor; when administration of a sympathomimetic amine is contraindicated.
Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Concerns related to adverse effects:
• Abnormal thinking/behavioral changes: Abnormal thinking and behavior changes have been reported and may include aggressive behavior, agitation, confusion, delirium, delusions, disorientation, paranoid ideation, and psychotic-like behavior.
• Diarrhea: Has been associated with delayed development of diarrhea (usual onset after 4 to 12 weeks); use with caution in patients with lower gastrointestinal disease or an increased risk of dehydration. Diarrhea may be a sign of drug-induced colitis (primarily lymphocytic). Monitor for weight loss. Discontinue use with prolonged diarrhea.
• Dyskinesia: New-onset or exacerbation of preexisting dyskinesia may occur when used as an adjunct to levodopa. Decreasing the dose of levodopa may ameliorate these side effects in some cases.
• Hallucinations: May cause hallucinations.
• Impulse control disorders: Compulsive behaviors and/or loss of impulse control, which has manifested as pathological gambling, libido increases (hypersexuality), intense urges to spend money uncontrollably, and other intense urges have been reported. Dose reduction or discontinuation of therapy has been reported to reverse these behaviors in some, but not all cases.
• Melanoma: Risk for melanoma development is increased in Parkinson disease patients; drug causation or factors contributing to risk have not been established. Patients should be monitored closely and periodic skin examinations should be performed. The Canadian labeling contraindicates use in patients with suspicious, undiagnosed skin lesions or history of melanoma.
• Neuroleptic malignant syndrome: Entacapone, in conjunction with other drug therapy that alters brain biogenic amine concentrations (eg, MAO inhibitors, SSRIs), has been associated with a syndrome resembling neuroleptic malignant syndrome (hyperpyrexia and confusion - some fatal) on abrupt withdrawal or dosage reduction. Concomitant use of entacapone and nonselective MAO inhibitors should be avoided.
• Orthostatic hypotension: May cause orthostatic hypotension and syncope.
• Pleural/retroperitoneal fibrosis: Dopaminergic agents from the ergot class have been associated with fibrotic complications, such as retroperitoneal fibrosis, pulmonary infiltrates or pleural effusion and thickening. These complications may resolve when the drug is discontinued, but complete resolution does not always occur. It is unknown whether nonergot, pro-dopaminergic agents like entacapone confer this risk.
• Rhabdomyolysis: Severe rhabdomyolysis has been reported with use.
• Somnolence: Patients have reported falling asleep while engaging in activities of daily living; this has been reported to occur without significant warning signs and may occur as late as up to 1 year after initiation of treatment. Monitor for daytime somnolence or preexisting sleep disorder. Use caution in the presence of sleep disorders, with other CNS depressants, sedating agents, psychoactive drugs or ethanol. Patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).
Disease-related concerns:
• Cardiovascular disease: The Canadian product labeling notes to use with caution in patients with cardiovascular disease, including a history of myocardial infarction (MI) and arrhythmias; MI and other ischemic adverse events have been observed in clinical trials.
• Hepatic impairment: Use with caution in patients with hepatic impairment or biliary obstruction. The Canadian labeling contraindicates use in hepatic impairment.
• Psychotic disorders: Avoid use in patients with major psychotic disorder due to the risk of exacerbating psychosis. Many treatments for psychosis may exacerbate the symptoms of Parkinson disease and may also decrease the effectiveness of entacapone.
Concurrent drug therapy issues:
• Sedatives: Effects with other sedative drugs or ethanol may be potentiated.
Other warnings/precautions:
• Discontinuation of therapy: Do not withdraw therapy abruptly.
• Urine discoloration: Urine may appear dark in color (brownish orange) during therapy.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Tablet, Oral:
Comtan: 200 mg [DSC] [contains polysorbate 80]
Generic: 200 mg
Yes
Tablets (Entacapone Oral)
200 mg (per each): $3.95 - $4.54
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Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Comtan: 200 mg [contains polysorbate 80]
Generic: 200 mg
Always administer in association with levodopa/carbidopa; can be combined with both the immediate and sustained release formulations of levodopa/carbidopa. May be administered without regard to meals. Should not be abruptly withdrawn from patient's therapy due to significant worsening of symptoms.
Parkinson disease: Adjunct to levodopa/carbidopa therapy in patients with idiopathic Parkinson disease who experience “wearing-off” symptoms at the end of a dosing interval
Inhibits COMT;
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
CNS Depressants: Entacapone may increase CNS depressant effects of CNS Depressants. Risk C: Monitor
COMT Substrates: COMT Inhibitors may increase serum concentration of COMT Substrates. Risk C: Monitor
Fluorodopa F18: Coadministration of COMT Inhibitors and Fluorodopa F18 may alter diagnostic results. Management: Discontinue medications used to treat Parkinson disease, including peripheral COMT inhibitors, 12 hours prior to fluorodopa F 18 administration if these medications can be safely withheld. Risk D: Consider Therapy Modification
Iron Preparations: May decrease serum concentration of Entacapone. Management: Consider separating doses of the agents by 2 or more hours to minimize the effects of this interaction. Monitor for decreased therapeutic effects of levodopa during concomitant therapy, particularly if doses cannot be separated. Risk D: Consider Therapy Modification
Lofepramine: Entacapone may increase adverse/toxic effects of Lofepramine. Risk X: Avoid
Monoamine Oxidase Inhibitors: COMT Inhibitors may increase adverse/toxic effects of Monoamine Oxidase Inhibitors. Management: Avoid coadministration of COMT inhibitors and nonselective monoamine oxidase inhibitors (MAOIs) (eg, isocarboxazid, phenelzine, tranylcypromine, linezolid, methylene blue) whenever possible. Risk D: Consider Therapy Modification
Tiapride: Entacapone may decrease therapeutic effects of Tiapride. Tiapride may decrease therapeutic effects of Entacapone. Management: If treatment with tiapride cannot be avoided in a patient with Parkinson disease, discontinuation of entacapone should be done gradually to minimize the risk for neuroleptic malignant syndrome. Risk D: Consider Therapy Modification
Warfarin: Entacapone may increase serum concentration of Warfarin. Specifically, entacapone may increase levels of the less potent R-enantiomer of warfarin Risk C: Monitor
Entacapone has been reported to chelate iron and decreasing serum iron levels were noted in clinical trials; however, clinically significant anemia has not been observed.
The incidence of Parkinson disease in pregnancy is relatively rare and information related to the use of entacapone in pregnant women is very limited (Kranick 2010; Tüfekçioğlu 2018).
It is not known if entacapone is present in breast milk.
The manufacturer recommends that caution be exercised when administering entacapone to breast-feeding women.
Signs and symptoms of Parkinson's disease; liver function tests, blood pressure, patient's mental status and impulse control disorders; daytime sleepiness; serum iron (if signs of anemia); weight loss (patients experiencing diarrhea); signs and symptoms of neuroleptic malignant syndrome if abrupt discontinuation required; dermatologic examination (regularly while on therapy).
Canadian labeling (additional monitoring recommendations): Cardiac function with initial dosage adjustments and periodically during prolonged therapy (patients with history of MI or arrhythmia)
Entacapone is a reversible and selective inhibitor of catechol-O-methyltransferase (COMT). When entacapone is taken with levodopa, the pharmacokinetics are altered, resulting in more sustained levodopa serum levels compared to levodopa taken alone. The resulting levels of levodopa provide for increased concentrations available for absorption across the blood-brain barrier, thereby providing for increased CNS levels of dopamine, the active metabolite of levodopa.
Onset of action: Rapid
Absorption: Rapid
Distribution: IV: Vdss: 20 L
Protein binding: 98%, primarily to albumin
Metabolism: Isomerization to the cis-isomer, followed by direct glucuronidation of the parent and cis-isomer
Bioavailability: 35%
Half-life elimination: Beta phase: 0.4 to 0.7 hours; gamma phase: 2.4 hours
Time to peak, serum: 1 hour
Excretion: Feces (90%); urine (10%)
Hepatic function impairment: AUC and Cmax are approximately 2-fold higher in those with a history of alcoholism and hepatic impairment.
