BACKGROUND: Vancomycin is frequently used as a prophylactic antibiotic in patients undergoing cardiac and orthopedic surgical procedures. However, the interactions of vancomycin with non-depolarizing muscle relaxant have not yet been reported on. Therefore, we studied the effects of vancomycin on the neuromuscular block of vecuronium, rocuronium and atracurium in vitro.

METHODS: Square wave, 0.1 Hz supramaximal stimuli were applied to the phrenic nerve-hemidiaphragm preparation of the rat and the twitch height response was recorded. We measured cumulative concentration response curves of vecuronium, rocuronium or atracurium, respectively, and also those of the rats that were pretreated with vancomycin (20 µgram/ml). The EC₅₀ and EC₉₅ of these muscle relaxants alone and those of the rats pretreated with vancomycin were calculated with using an inhibitory sigmoid Emax model.

RESULTS: Vancomycin alone did not depress the twitch height. The pretreated vancomycin (20 µgram/ml) did not affect the EC₅₀ and EC₉₅ of vecuronium or rocuronium, but it significantly reduced the EC₅₀ and EC₉₅ of atracurium (P < 0.05).

CONCLUSIONS: Vancomycin itself does not have neuromuscular blocking properties. Vancomycin does not affect the neuromuscular blockade induced by vecuronium or rocuronium, but it significantly enhances the neuromuscular blockade induced by atracurium.