Entacapone


Concise Prescribing Info
Indications/Uses
Adjunct to levodopa treatment in Parkinson's disease.
Dosage/Direction for Use
Adult : PO 200 mg w/ each levodopa/dopa decarboxylase inhibitor dose. Max: 200 mg 10 times/day.
Dosage Details
Oral
Adjunct to levodopa treatment in Parkinson's disease
Adult: 200 mg w/ each levodopa/dopa decarboxylase inhibitor dose. Max: 200 mg 10 times daily (2,000 mg daily). Gradually reduce levodopa dose by approx 10-30% or increase dosing interval w/in the 1st few wk of starting treatment.
Hepatic Impairment
Contraindicated.
Administration
May be taken with or without food.
Contraindications
Phaeochromocytoma, history of neuroleptic malignant syndrome and/or non-traumatic rhabdomyolysis. Hepatic impairment. Concomitant use w/ non-selective MAOIs.
Special Precautions
Patient w/ biliary obstruction, ischaemic heart disease. Avoid abrupt withdrawal. Pregnancy and lactation.
Adverse Reactions
Abdominal pain, nausea, vomiting, diarrhoea, constipation, colitis, dry mouth, dyskinesia, dizziness, nightmares, insomnia, hallucinations, confusion, fatigue, increased sweating, behavioural disturbances; urine, skin, hair, beard and nail discolourations; cholestatic hepatitis, rhabdomyolysis. Rarely, agitation, urticaria, erythematous or maculopapular rash, anorexia, wt decrease, increased liver enzymes.
Potentially Fatal: Neuroleptic malignant syndrome (NMS)-like syndrome (w/ abrupt reduction or withdrawal).
Patient Counseling Information
This drug may cause reddish-brown discolouration of urine. When given w/ levodopa, may cause dizziness and symptomatic orthostatism, if affected, do not drive or operate machinery.
MonitoringParameters
Monitor BP, hepatic function, mental status and impulse control disorders, daytime sleepiness, serum Fe, wt loss; signs/symptoms of Parkinson's disease, neuroleptic malignant syndrome (if abrupt withdrawal is required); regular dermatologic examination.
Overdosage
Symptoms: Decreased activity, confusion, somnolence, hypotonia, urticaria, skin discolouration. Management: Symptomatic treatment.
Drug Interactions
May interfere w/ metabolism of other drugs metabolised by COMT (e.g. rimiterole). May aggravate levodopa-induced orthostatic hypotension. Risk of dopaminergic effects w/ dopamine agonists (e.g. bromocriptine), selegiline, amantadine. May form chelates w/ Fe in the GI tract. Additive sedative effects w/ other CNS depressants.
Potentially Fatal: Concomitant use w/ non-selective MAOIs (e.g. phenelzine) may result in inhibition of principal pathways in the metabolism of catecholamines.
Food Interaction
May potentiate the sedative effect of alcohol.
Action
Description: Entacapone decreases the metabolic loss of levodopa to 3-O-methyldopa (3-OMD) through inhibition of COMT enzyme leading to an increased levodopa concentration, thus, extending the duration and effect in the brain.
Pharmacokinetics:
Absorption: Rapidly absorbed from the GI tract. Bioavailability: 29-46%. Time to peak plasma concentration: Approx 1 hr.
Distribution: Plasma protein binding: Approx 98% (primarily to albumin).
Metabolism: Undergoes extensive first-pass metabolism; isomerisation to the cis-isomer, followed by direct glucuronidation of the parent and cis-isomer.
Excretion: Mainly via faeces (10%); urine (approx 10-20%, as glucuronide conjugates). Elimination half-life: Approx 1.6-3.4 hr.
Chemical Structure

Chemical Structure Image
Entacapone

Source: National Center for Biotechnology Information. PubChem Database. Entacapone, CID=5281081, https://pubchem.ncbi.nlm.nih.gov/compound/Entacapone (accessed on Jan. 21, 2020)

Storage
Store at 25°C.
ATC Classification
N04BX02 - entacapone ; Belongs to the class of other dopaminergic agents used in the management of Parkinson's disease.
References
Anon. Entacapone. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 27/11/2015.

Buckingham R (ed). Entacapone. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 27/11/2015.

Comtan Tablet, Film Coated (Novartis Pharmaceuticals Corporation). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 27/11/2015.

McEvoy GK, Snow EK, Miller J et al (eds). Entacapone. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 27/11/2015.

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