GABAPENTIN FOR PARKINSONISM - A DOUBLE-BLIND, PLACEBO-CONTROLLED, CROSSOVER TRIAL

PURPOSE: Gabapentin is a recently available anticonvulsant whose mecha nism of action remains unknown. We suspected efficacy from serendipito us observations of gabapentin in patients with parkinsonism. This led us to a double-blind, placebo-controlled, crossover trial. PATIENTS AN D METHODS: We administered gabapentin in a placebo-controlled, double- blind, crossover trial to 19 subjects with advanced parkinsonism. We m easured the effect of placebo and gabapentin on subjects' symptoms wit h the Unified Parkinson's Disease Rating Scale, the Webster Scale, and the Hoehn and Yahr Scale, We assessed tremor with surface-recorded el ectromyography. RESULTS: Total Unified Parkinson's Disease Rating Scal e improved with gabapentin compared with placebo (P = 0.0005). Likewis e, activities of daily living and examination subscore of the Unified Parkinson's Disease Rating Scale improved with gabapentin compared wit h placebo but did not achieve statistical significance. Webster Scale showed improvement but neither Hoehn and Yahr Scale nor Webster Scale changes reached statistical significance. Tremor as measured by the Un ified Parkinson's Disease Rating Scale improved with gabapentin but th e use of the root mean square of the rectified electromyography as a m easure of tremor activity was not statistically significant. CONCLUSIO NS: This study demonstrates that gabapentin improves rigidity, bradyki nesia, and tremor of parkinsonism including both Parkinson's disease a nd Parkinson's syndrome. The rigidity and bradykinesia of parkinsonism improve on the drug even when the effects of gabapentin on tremor are discounted.