Atracurium and Vecuronium: Two Unique Neuromuscular Blocking Agents

Atracurium and vecuronium are two new nondepolarizing skeletal muscle relaxants that were developed to overcome the deficiencies seen with currently available agents (tubocurarine, metocurine, pancuronium, and gallamine). Both compounds have unique metabolic profiles, separating them from other nondepolarizing agents. Neigher drug depends on normal renal function for excretion and each can safely be given to patients with renal failure. Atracurium also does not depend on hepatic function for metabolism; however, vecuronium may require dosing adjustments in hepatic disease. Atracurium and vecuronium have similar onset times for muscle relaxation but shorter durations of action than other nondepolarizing muscle relaxants. Both agents produce minimal cumulative effects with repeated doses. A major advantage of both agents is their relative lack of cardiovascular effects when given in clinically effective doses, differing from other nondepolarizing muscle relaxants. Both agents produce a lower degree of histamine release than other agents, although atracurium appears to produce a higher incidence of histamine-like reactions than vecuronium. Vecuronium appears to be the agent of choice in patients with a history of asthma or allergy. The place in therapy for these new agents is discussed.