Succinylcholine commonly produces frequent adverse effects, including muscle fasciculation and myalgia. The current study identified the optimal dose of rocuronium to prevent succinylcholine-induced fasciculation and myalgia and evaluated the influence of rocuronium on the speed of onset produced by succinylcholine.

This randomized, double-blinded study was conducted in 100 patients randomly allocated into five groups of 20 patients each. Patients were randomized to receive 0.02, 0.03, 0.04, 0.05 and 0.06 mg/kg rocuronium as a precurarizing dose. Neuromuscular monitoring after each precurarizing dose was recorded from the adductor pollicis muscle using acceleromyography with train-of-four stimulation of the ulnar nerve. All patients received succinylcholine 1.5 mg/kg at 2 minutes after the precurarization, and were assessed the incidence and severity of fasciculations, while myalgia was assessed at 24 hours after surgery.

The incidence and severity of visible muscle fasciculation was significantly less with increasing the amount of precurarizing dose of rocuronium (P < 0.001). Those of myalgia tend to decrease according to increasing the amount of precurarizing dose of rocuronium, but there was no significance (P = 0.072). The onset time of succinylcholine was significantly longer with increasing the amount of precurarizing dose of rocuronium (P < 0.001).

Precurarization with 0.04 mg/kg rocuronium was the optimal dose considering the reduction in the incidence and severity of fasciculation and myalgia with acceptable onset time, and the safe and effective precurarization.