Entacapone

OBJECTIVE: To introduce entacapone, a new catechol- O-methyltransferase inhibitor, and discuss its pharmacology, pharmacodynamics, pharmacokinetics, clinical efficacy, drug interactions, adverse events, dosage guidelines, and therapeutic and formulary considerations. DATA SOURCE: A MEDLINE database search (1966–December 1999) was performed to identify relevant English-language articles including recent studies, abstracts, and reviews. Search terms included entacapone, OR-611, catechol- O-methyltransferase inhibitor, and Parkinson's disease. STUDY SELECTION: Relevant published human studies were chosen to summarize the pharmacokinetics, clinical efficacy, adverse effects, and drug interactions. DATA EXTRACTION: All available human clinical trials were reviewed. DATA SYNTHESIS: Entacapone is the second medication of a new class of drugs, the catechol- O-methyltransferase inhibitors, indicated for clinical use as an adjunct to levodopa/carbidopa to treat patients with idiopathic Parkinson's disease who experience the signs and symptoms of end-of-dose wearing-off. Entacapone in combination with levodopa/dopa decarboxylase inhibitor has been shown to increase the AUC of levodopa, which leads to less fluctuation of levodopa plasma concentrations. Clinically, the duration of motor response to levodopa was prolonged as reflected by an increase in the mean on time. The addition of entacapone resulted in a decrease in the mean daily dosage of levodopa. The recommended dosage of entacapone is 200 mg administered orally with each dose of levodopa/carbidopa, up to a maximum of eight doses per day. Common adverse effects include dyskinesia, nausea, diarrhea, and urine discoloration. CONCLUSIONS: Entacapone should be considered as add-on treatment to levodopa/carbidopa in Parkinson's disease patients with end-of-dose wearing-off effect.