Entacapone enhances the response to levodopa in parkinsonian patients with motor fluctuations

Abstract

To study the effect and safety of entacapone as an adjunct to levodopa treatment in patients with PD with wearing-off motor fluctuations. Entacapone is a catechol-O-methyltransferase (COMT) inhibitor that has been shown to increase the area under the concentration-time curve of plasma levodopa by decreasing its systemic elimination, thereby promoting and improving therapeutic response to it. A total of 171 parkinsonian patients with wearing-off-type motor fluctuations participated in a 6-month randomized, placebo-controlled, double-blind, parallel-group study. The extent of therapeutic response was elicited in the first hand with home diary recordings of "on" and "off" times by the patient and with Unified Parkinson's Disease Rating Scale scoring by the examiner. The patients took either 200 mg entacapone or identical placebos concomitantly with each daily levodopa dose (four to 10 times a day). Patients' home diaries indicated that entacapone increased the mean (+/- SD) "on" time significantly (9.3 +/- 2.2 to 10.7 +/- 2.2 hours; p < 0.01) and correspondingly decreased the "off" time significantly (5.3 +/- 2.2 to 4.2 +/- 2.2 hours; p < 0.001). The average benefit derived from a daily levodopa dose as related by the patients was increased significantly (p < 0.01). The daily levodopa dose was reduced significantly in the entacapone group, the difference between the groups being 102 mg (p < 0.01). The entacapone-derived increase in the benefit from levodopa was lost almost completely following its withdrawal. Entacapone was well tolerated. Dopaminergic adverse events, which increased, were ameliorated by reducing the levodopa dose. Diarrhea was the most common nondopaminergic adverse event. Long-term entacapone treatment effectively prolonged the beneficial response to levodopa in parkinsonian patients with the wearing-off phenomenon. The improvement occurred irrespective of the reduction of the levodopa dose.