The catechol-O-methyltransferase (COMT) inhibitor entacapone enhances the pharmacokinetic and clinical response to Sinemet CR in Parkinson's disease

Objectives-Entacapone is a specific, potent, peripherally acting catechol-O-methyltransferase (COMT) inhibitor. It has been shown to improve the bioavailability of plasma levodopa and extend its clinical effect when used as an adjunct to standard levodopa preparations, but there is little experience of the effect of entacapone on controlled release levodopa preparations. Methods-A double blind, placebo controlled, single dose, randomised, cross over trial was performed in 14 patients with Parkinson's disease with motor fluctuations to investigate the clinical effect of a single dose of entacapone (200 mg) when administered with either standard levodopa-carbidopa (Sinemet(TM)) or controlled release levodopa-carbidopa preparations (Sinemet CRTM). Results-When entacapone was administered with standard Sinemet(TM) the duration of the clinical response to standard Sinemet(TM) was longer in comparison with the response after placebo (p=0.02). Moreover, in the same patients, entacapone significantly increased the duration of the clinical response to Sinemet CRTM (p=0.05) without prolonging the latency of response or enhancing dyskinesias. Conclusions-These data confirm the clinical efficacy of entacapone-standard Sinemet(TM) combination. They also indicate that adding entacapone to controlled release levodopa preparations might provide a useful treatment option in patients with Parkinson's disease with motor fluctuations. A double blind clinical. trial with a chronically administered entacapone-Sinemet CRTM combination is, however, required to verify this viewpoint.