Entacapone
Pronouncation: (en-TACK-ah-pone)Class: Antiparkinson agent
Trade Names:
Comtan
- Tablets 200 mg
Pharmacology
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The exact mechanism of action is unknown. Inhibits catechol-O-methyl transferase (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.
Pharmacokinetics
Absorption
Rapidly absorbed. T max is approximately 1 h. C max is approximately 1.2ߙmcg/mL (single 200ߙmg dose).
Distribution
Vd is 20 L (IV). 98% is protein bound, mainly to albumin.
Metabolism
Almost completely metabolized; inactive metabolites formed by isomerization and glucuronidation.
Elimination
Approximately 10% is excreted in the urine (0.2% as unchanged drug) and 90% in feces.
Special Populations
Hepatic Function ImpairmentAUC and C max are approximately 2-fold higher in those with a a history of alcoholism and hepatic function impairment.
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.”
Contraindications
Standard considerations.
Dosage and Administration
AdultsPO 200 mg concomitantly with each levodopa/carbidopa dose to max 8 times/day.
Storage/Stability
Store at room temperature (15° to 30° C [59° to 86°F]) in tightly closed containers.
Drug Interactions
Ampicillin, cholestyramine, chloramphenicol, erythromycin, probenecid, rifampinMay interfere with biliary excretion or metabolism of entacapone.
Apomorphine, bitolterol, dobutamine, dopamine, epinephrine, isoetherine, isoproterenol, methyldopa, norepinephrineExcessive changes in BP, increased heart rate, and arrhythmias may occur.
Laboratory Test Interactions
May decrease iron stores by chelation of iron.
Adverse Reactions
CNS
Dyskinesia; hyperkinesia; hypokinesia; dizziness; anxiety; somnolence; agitation; hallucinations.
EENT
Taste perversion.
GI
Nausea; diarrhea; abdominal pain; constipation; vomiting; dry mouth; dyspepsia; flatulence; gastritis.
Genitourinary
Urine discoloration.
Hematologic
Purpura.
Respiratory
Dyspnea.
Miscellaneous
Sweating; back pain; fatigue; asthenia.
Precautions
Pregnancy
Category C .
Lactation
Undetermined.
Children
Safety and efficacy not established.
Hepatic impairment or biliary obstruction
Use with caution.
Hyperpyrexia and confusion
Exercise caution. Rhabdomyolysis and symptom complex resembling neuroleptic malignant syndrome reported in association with therapy.
MAOIs
Avoid concurrent use of nonselective MAOIs (ie, isocarboxazid, phenelzine, tranylcypromine). Administration of MAOIs may result in inhibition of the majority of pathways for catecholamine metabolism.
Overdosage
Symptoms
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, syncope, and sweating 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 to neither drive a car, operate other complex machinery, or engage in any hazardous activity until sure entacapone does not affect mental or motor performance.
- Inform patient that nausea or hypotension may occur, especially at the initiation of treatment.
- Advise patients of the possibility of an increase in dyskinesia.
- 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 primary caregiver if becoming pregnant, planning to become pregnant, or breastfeeding.
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More Entacapone resources:
Entacapone - Includes detailed dosage instructions.
