Metabolism and kinetics of atracurium: an overview.

Atracurium, a new competitive neuromuscular blocking agent, is broken down in the body by two mechanisms, Hofmann elimination and ester hydrolysis. Chemical breakdown by Hofmann elimination is rapid at physiological pH and temperature, whereas ester hydrolysis is enzyme-catalysed but by enzymes other than pseudocholinesterase. The products of these reactions have been shown to lack neuromuscular or cardiovascular activity at the concentrations occurring after therapeutic doses of atracurium. Studies with radiolabelled drug in anaesthetized cats have shown that atracurium and its metabolites are readily excreted in bile and urine. Plasma kinetics are unaltered if renal function is negated by bilateral ligation of all renal blood vessels. Preliminary studies have indicated that atracurium does not cross the placenta to a significant extent and that the drug can be used safety in Caesarean section.