Effects of Phenytoin and Carbamazepine on Rocuronium-Induced Partial Neuromuscular Blockade

ABSTRACT

BACKGROUND: Phenytoin and carbamazepine may augment a neuromuscular block from nondepolarizing muscle relaxants. The potency of rocuronium is increased after the administration of an acute high dose of phenytoin. We investigated the effects of phenytoin and carbamazepine on rocuronium-induced neuromuscular blockade. METHODS: Male Sprague Dawley rats (n = 80) were randomly allocated into a control group, phenytoin group, carbamazepine group, and phenytoin with carbamazepine group. The phrenic nerve was stimulated with supramaximal intensity and twitch responses were measured. After a stabilization period, 300microg rocuronium was added. After 10 minutes, in the pheytoin group of rats, phenytoin in Krebs solution was administered at a concentration of 1microg/ml (P1), 10microg/ml (P10) and 100microg/ml (P100). In the carbamazepine group of rats, carbamazepine in Krebs solution was administered at a concentration of 0.5microg/ml (C0.5), 5microg/ml (C5) and 50microg/ml (C50). In the phenytoin with carbamazepine group of rats, phenytoin simultaneously with carbamazepine was administered in Krebs solution at a phenytoin concentration of 10microg/ml (P10) and a carbamazepine concentration of 5microg/ml (C5). We measured twitch responses at 10 minutes after rocuronium administration and 10 minutes after the administration of the anticonvulsants. RESULTS: There were significant depressions in the twitch response of rocuronium in the 100microg/ml phenytoin group of rats, 5microg/ml and 50microg/ml carbamazepine group of rats, and the 10microg/ml phenytoin with 5microg/ml carbamazepine group of rats. CONCLUSIONS: The potency of rocuronium increased with phenytoin and carbamazepine administration. Phenytoin and carbamazepine can cause recurarization perioperatively.