ABSTRACT
Atracurium, one of the newly developed nondepolarizing muscle relaxants, is remarkable due to the intermediate duration of action from the other previously known nondepolarizing agents and the broad safety margin in patients with renal or liver disease. There have been many reports suggesting that the pharmacologic effects of the nondepolarizing muscle relaxants are influenced by dosage. In this study, we attempted to identify the specific mechanism of muscle relaxation of atracurium. Particular attention was paid to the actually delivered atracurium dose and to the degree of muscle relaxation in rabbits. The results were as follows; 1) In the atracurium 0.4 mg/kg group, the onset of action was shortened and in the atracurium 0.6 mg/kg group, it was shortened more significantly. 2) The duration of action was increased with the increase of dose: the mean duration was 895 seconds in the atracurium 0.1 mg/kg group, 1,113.7 seconds in the 0.2 mg/kg group, and 1,199.3 second is in the 0.4 mg/kg group. It was prolonged to 1,730 seconds in the atracurium 0.6mg/kg group. 3) The spontaneous recovery index showed no differences in the atracurium 0.1 mg/kg group, 0.2 mg/kg group and 0.4 mg/kg group (196.7 sec., 195.0 sec, 202.7 sec. each). But in the atracurium 0.6 mg/ kg group, it was markedly prolonged to 334 seconds. In conclusion, atracurium, like other nondepolarizing agents, produces a dose related duration of action in muscle relaxation.