Diphenylhydantoin-lnduced Asterixis

While asterixis has recently been reported in connection with diphenylhydantoin intoxication, this clinical sign is not widely recognized as a symptom of such intoxication. We present two cases in which asterixis and multiple myoclonus occurred when serum diphenylhydantoin levels reached the toxic range. The movement disorder disappeared when diphenylhydantoin levels decreased. Controlled overdose reproduced the disorder in both patients. Metabolism of diphenylhydantoin and ammonia appeared to be normal in these patients. Asterixis is a potential symptom of diphenylhydantoin intoxication. (JAMA229:538-540, 1974)