Ipenoxazone is a potent and centrally acting muscle relaxant. An intravenous injection of 2 mg/kg Ipenoxazone causes a reduction of electromyographic activity which reaches a maximum within 3 min after the injection. Within 1 min after the injection of Ipenoxazone at a dose of 4 mg/kg, the blood pressure changes from a control level of 138±9 mmHg to a minimum level of 98±9 mmHg (n=6) but it rapidly returns to the control level within 1 to 2 min, while the rigidity is still reduced significantly at that time. High doses (greater than 30 mg/kg i.p.) of Ipenoxazone produces a transient and dose-dependent sedation in almost all mice about 5 min after its administration.