A study of the anticholinesterase and anticurare effects of some cholinesterase inhibitors.

SUMMARY The inhibition of serum cholinesterase by neostigmine, tacrine, pyridostigmine and edrophonium has been measured in vivo under clinical conditions. The inhibition by these agents of both serum cholinesterase and red blood cell cholinesterasehas been compared in vitro. The anticurare action of neostigmine and of tacrine has been compared myographically. Previousclinical observations have been confirmed, and further support is given to the theory that neostigmine has a direct actionon the neuromuscular junction or muscle fibre, apart from its anticholinesterase property. However, the degree of inhibition of the enzyme depends upon the concentrations of enzyme, substrate and inhibitor, and since the concentrations existing at the neuromuscular junction are unknown, they cannot be reproduced for experimental purposes.