Cholinesterase Inhibitors: Edrophonium

EDROPHONIUM

Physical Structure

Because it lacks a carbamate group, edrophonium must rely on noncovalent bonding to the acetyl-cholinesterase enzyme. The quaternary ammonium group limits lipid solubility.

Dosage & Packaging

Edrophonium is less than 10% as potent as neostig-mine. The recommended dosage is 0.5–1 mg/kg. Edrophonium is available as a solution containing 10 mg/mL; it is available with atropine as a combi-nation drug (Enlon-Plus; 10 mg edrophonium and 0.14 mg atropine per mL).

Clinical Considerations

Edrophonium has the most rapid onset of action (1–2 min) and the shortest duration of effect of any of the cholinesterase inhibitors. Reduced doses should not be used, because longer-acting muscle relaxants may outlast the effects of edrophonium. Higher doses prolong the duration of action to more than 1 hr. Edrophonium may not be as effective as neostigmine at reversing intense neuromuscular blockade. In equipotent doses, muscarinic effects of edrophonium are less pronounced than those of neostigmine or pyridostigmine, requiring only half the amount of anticholinergic agent. Edrophonium’s rapid onset is well matched to that of atropine (0.014 mg of atropine per 1 mg of edrophonium). Although glycopyrrolate (0.007 mg per 1 mg of edrophonium) can also be used, it should be given several minutes prior to edrophonium to avoid the possibility of bradycardia.