BACKGROUND: Subparalyzing doses of nondepolarizing muscle relaxants are often given prior to succinylcholine to reduce the adverse effects of succinylcholine. We designed this study to determine the optimal choice of nondepolarizing muscle relaxants and the optimal interval between pretreatment and succinylcholine administration.

METHODS: 240 ASA I or II adult patients were randomized into six groups: groups V1.5 and V3 received 0.015 mg/kg of vecuronium 1.5 min and 3 min before succinylcholine; group R1, R1.5, and R3 received 0.09 mg/kg of rocuronium 1 min, 1.5 min and 3 min before succinylcholine; and group SCC received no pretreatment. In this study, 2 mg/kg of succinylcholine was used. The presence and severity of fasciculations and intubating conditions were evaluated. Myalgia was also recorded on postoperative days 1 and 2.

RESULTS: Group R3 was significantly better than other groups in terms of preventing fasciculations, and was followed by groups R1.5, R1, V3, V1.5 and group SCC. Intubating conditions were significantly worse in all pretreated groups than in group SCC, but no significant differences were observed between the pretreated groups.

CONCLUSIONS: Succinylcholine-induced fasciculations are effectively prevented by pretreating with rocuronium 3 min or 1.5 min prior to succinylcholine administration. However intubating conditions are worsened by pretreatments.