Paradoxical Reactions to Benzodiazepines — A Genetically Determined Phenomenon?

Benzodiazepines are used for their anxiolytic, sedative, amnesic, anticonvulsant, and muscle relaxant properties.However, occasionally paradoxical effects occur following their administration.Those described include restlessness, agitation or increased anxiety, aggression and rage, depression, and fits.1,2 When benzodiazepines are used to provide sedation for minor surgical procedures, we have occasionally observed patients who become restless, with spontaneous muscle movements rather than displaying the relaxation and sedation typical of benzodiazepine action.We report the cases of a pair of monozygotic twins who exhibited this atypical response. Case ReportsThe twins were fit, 28-year-old males, taking no medication, who were volunteers in a laboratory study of benzodiazepine potency.The first twin after receiving midazolam 5 mg intravenously, became drowsy but restless, with frequent yawning and constant movement of arms and legs.His arms appeared to move in a stereotyped fashion, from hands behind head, to hands on hips, to rubbing nose, to arms folded, etc.A second 'M.