Rapacuronium administration to patients receiving phenytoin or carbamazepine

Patients receiving anticonvulsants such as phenytoin or carbamazepine may be resistant to neuromuscular blocking agents. The authors report the response to rapacuronium bromide (1.5 mg/kg) in two adult patients; one receiving phenytoin and the other receiving carbamazepine. In both patients, there was a delay in achieving maximum blockade; 100% depression of the first twitch was never achieved in the patient receiving phenytoin. Recovery of neuromuscular function was rapid. In the patient receiving phenytoin and carbamazepine respectively, the clinical duration (time to return of T1% to 25% of baseline) was 5 and 9 minutes, the recovery index (T1 25%-75%) was 4 minutes and 3 minutes, and the time to return of T4/T1 to greater than 0.7 was 15 minutes and 18 minutes 40 seconds. As has been reported with other neuromuscular blocking agents of the aminosteroid class, the clinical duration and the recovery index of rapacuronium are shortened in patients receiving either phenytoin or carbamazepine.