Marked amelioration of alcohol-responsive posthypoxic myoclonus by gamma-hydroxybutyric acid (Xyrem).

We conducted an open-label, dose-finding, blinded-rating trial of gamma-hydroxybutyric acid (Xyrem) in a single patient with severe alcohol-responsive posthypoxic myoclonus refractory to treatment with standard antimyoclonic agents. Xyrem was given in divided doses during the day and was well tolerated. Intensity of myoclonus was measured using the Unified Myoclonus Rating Scale, and blinded videotape review demonstrated complete resolution of myoclonus at rest and stimulus-sensitive myoclonus. Action myoclonus and functional performance also improved in ways that were practically meaningful, allowing her to feed herself, to accomplish daily hygiene tasks, and to walk with assistance. The possible mechanisms of action and potential uses of this agent in other alcohol-responsive movement disorders are discussed.