Rocuronium bromide is a monoquaternary amino steroidal muscle relaxant. Rocuronium is structurally stable and no metabolites of rocuronium have not been observed in humans. The manufacturer recommends that rocuronium can be stored in room temperature for 12 weeks. The aim of this study was to determine if the storage temperature of rocuronium could influence the pharmacodynamics of rocuronium.

One hundred of patients with a class I or II ASA physical status were enrolled in this study. It was divided to two groups. One (Group '0', n = 50) consists of those who had intravenously administered the rocuronium which had been stored in refrigerator and the other (Group '14', n = 50) consists of those who had intravenously administered the rocuronium which had been stored in room temperature (20-29℃, median 25.1℃) for 14 days. Before an anesthesia was induced, TOF-Watch® was attached and calibrated. The anesthesia was induced with 1µg/kg of fentanyl and 1.5 mg/kg of propofol intravenously. While the 0.1 Hz of single twitch was applied, 0.45 mg/kg of rocuronium, which is appointed to each group, was injected. Intubation is performed 90 seconds after injection of rocuronium and evaluated the intubating condition as excellent, good, poor, and impossible.

There was a statistically significant difference in intubating condition at 90 seconds between two groups. The onset time to twitch depression of 0% in group '14' was prolonged compared to group '0' (P < 0.05). Clinical duration was also shortened in group '14' (P < 0.05).

Compared with the use of rocuronium stored in refrigerator, that stored at room temperature can be expected to have unfavorable intubating condition at 90 seconds after rocuronium injection. Therefore, the storage temperature has some influences on the efficacy of rocuronium.