Atracurium is degraded by both pH and temperature dependent Hofmann elimination (autolysis) and by ester hydrolysis; it therefore does not require a dosage adjustment in patients with renal or hepatic failure. However, acidosis and severe hypothermia decrease the rate of drug metabolism and should prompt dose reduction. Mivacurium is a sho-acting benzylisoquinoline with an onset of action comparable to atracurium but with one-third its duration of action, because of rapid hydrolysis by plasma pseudocholinesterase. However, patients with renal or hepatic insufficiency may have depressed pseudocholinesterase activity leading to delayed elimination. Vecuronium is an aminosteroid compound with an intermediate duration of action. It is hepatically metabolized to three active metabolites, all of which are eliminated by the kidney.