Doxacurium. A review of its pharmacology and clinical potential in anaesthesia.

Doxacurium, a benzylisoquinolinium diester, provides nondepolarising neuromuscular blockade (and thus surgical relaxation), without vagolytic or sympathomimetic effects. At equipotent doses, the duration of action of doxacurium is similar to that of the long-acting neuromuscular blocker pancuronium. Supplemental doses of doxacurium administered at approximately 25% recovery reliably increase the depth and duration of neuromuscular blockade without accumulation. Although patients will recover spontaneously from doxacurium neuromuscular blockade, pharmacological reversal with neostigmine is recommended in line with accepted clinical practice, and permits acceleration of recovery when necessary. Doxacurium may also be used to facilitate endotracheal intubation. However, even with large doses onset of action is delayed, suggesting more rapidly acting neuromuscular blocking agents will be preferred when rapid sequence induction and intubation is required. Doxacurium has been successfully used in children, the elderly, and in patients with renal failure, hepatic failure, or cardiovascular disease. The absence of clinically significant effects on cardiovascular parameters and relative lack of histamine release observed in clinical trials indicates that doxacurium is suitable for use in high-risk patient groups. Thus, while there are only a limited number of studies comparing doxacurium with other nondepolarising neuromuscular blockers, particularly other 'cardiostable' agents, its ability to produce sustained effective muscle relaxation without significantly affecting the cardiovascular system or inducing histamine release would seem to make it a preferred agent for surgery of longer duration, particularly in high-risk patient groups.