Rapacuronium administration to patients receiving phenytoin or carbamazepine

Patients receiving anticonvulsants such as phenytoin or carbamazepine may b e resistant to neuromuscular blocking agents. The authors report the respon se to rapacuronium bromide (1.5 mg/kg) in two adult patients; one receiving phenytoin and the other receiving carbamazepine. In both patients, there w as a delay in achieving maximum blockade; 100% depression of the first twit ch was never achieved in the patient receiving phenytoin. Recovery of neuro muscular function was rapid. In the patient receiving phenytoin and carbama zepine respectively, the clinical duration (time to return of T-1% to 25% o f baseline) was 5 and 9 minutes, the recovery index (T-1 25%-75%) was 4 min utes and 3 minutes, and the time to return of T-4/T-1 to greater than 0.7 w as 15 minutes and 18 minutes 40 seconds. As has been reported with other ne uromuscular blocking agents of the aminosteroid class, the clinical duratio n and the recovery index of rapacuronium are shortened in patients receivin g either phenytoin or carbamazepine.