The impact of remacemide hydrochloride on levodopa concentrations in Parkinson's disease. Parkinson Study Group

This study was designed to determine whether remacemide hydrochloride, a noncompetitive N-methyl-D-aspartate-type glutamate receptor channel blocker, has a significant impact on serum levodopa concentrations that could complicate the interpretation of future clinical trial results. We performed a multicenter, open-label study of remacemide in 18 patients with mild to moderate Parkinson's disease (PD) who were taking stable dosages of levodopa. Levodopa pharmacokinetics were determined after administration of the patients' usual morning levodopa dose. Patients then took remacemide 300 mg twice a day for 2 weeks, with levodopa pharmacokinetics determined again at an identical testing session, except that remacemide 300 mg was administered one hour before levodopa. Clinical responses were also measured using the Unified Parkinson's Disease Rating Scale (UPDRS). With remacemide treatment, the area-under-the-curve for levodopa did not change. The mean peak plasma levodopa concentration (Cmax) was reduced by 16% compared to baseline, and the mean time to achieve peak plasma levodopa concentration (Tmax) was delayed by 20%. Although remacemide delayed levodopa absorption, the magnitude of the interaction suggests that is unlikely to be an important factor in planning and interpreting future trials of remacemide in levodopa-treated patients with PD.