The inhibition of human motor endplate cholinesterase by anticholinesterase compounds was studied using isolated muscle membrane preparation. Ambenonium was most potent, and edrophonium was least potent in inhibiting motor endplate cholinesterase. The slope of the regression line for inhibition of motor endplate cholinesterase was greatest for ambenonium, and smallest for neostigmine and edrophonium. These compounds were less potent inhibitors of plasma cholinesterase. Ambenonium was more specific, and other compounds were less specific inhibitors of motor endplate cholinesterase. In myasthenic patients, these compounds produced adequate inhibition of motor endplate cholinesterase even in the presence of relatively mild plasma cholinesterase inhibition.
