Canadian Journal of Anesthesia, Vol 33, 332-335, Copyright © 1986 by Canadian Anesthesiologists' Society

The Inhibitory Effect of Esmolol on Human Plasmacholinesterase

¹ University of Illinois College of Medicine at Chicago, Department of Anesthesiology, 1740 West Taylor Street, Chicago, Illinois 60612, U.S.A.

correspondence should be addressed to Dr. Zsigmond.

Esmolol, a new cardioselective beta adrenergic blocker inhibits plasmacholinesterase activity in vitro. The concentration of esmolol hydrochloride that inhibits by 50 per cent the hydrolysis of 50.0 µmol·L^-1 benzoylcholine hydrochloride by 1:200 diluted, heparinized pooled plasma of six healthy volunteers at 37°C and 240 nm, determined by the ultraviolet spectrophotometric method of Kalow, was 50 µmol·L^-1 Esmolol's primary metabolite, 3-[4-(2-hydroxy-3-(isopropylamino)propoxy)-phenyl]propionic acid, had an I₅₀ = 190 µmpl·L^-1. The benzoylcholine hydrolysis rates in the plasma of ten patients who received an esmolol infusion of 500 µg·kg^-1·min^-l for 4 minutes were 58.6 ± 6.2 µmol·hr^-1·ml^-1 (mean ± SE) before and 55.1 ± 6.6 µmol·hr^-1·ml^-l after the infusion. The benzoylcholine hydrolysis rates in the plasma of ten patients who received an esmolol infusion of 500 µg·kg^-1·min^-1 for two minutes and 200 µg·kg^-1·min^-1 for an additional two minutes were 70.2 ± 8.9µmol·hr^-l·ml^-l before and 69.1 ± 9.5µmol·hr^-1·ml^-1 after the infusion. The pre- and post-infusion plasmacholinesterase activities were not significantly different. Since plasmacholinesterase is responsible for the hydrolysis of succinylcholine and that of the ester-type local anaesthetics this lack of in vivo interaction of esmolol with the hydrolysis of these drugs should be further confirmed by experiments with these combinations in man.

Key Words: ENZYMES: plasmacholinesterase, inhibition • NEUROMUSCULAR RELAXANTS: succinylcholine • SYMPATHETIC NERVOUS SYSTEM: sympatholytic agents: esmolol