Levin_1955_J.Pharmacol.Exp.Ther_113_206

Compounds 3113 CT and 3152 CT, which are chemically related to neostigmine, exhibit an I50(concentration necessary to produce 50 per cent inactivation) against erythrocyte cholinesterase, under specified conditions, of the order of l0-9 M. This figure is contrasted with values reported by Funke et al., namely 10-16 M and 10-14 M, respectively, for the I50 of these two compounds. The inactivation produced by these compounds may be reversed by repeated washing of the erythrocytes. On the basis of current concepts of interaction between cholinesterases and anticholinesterases, and a knowledge of the concentration of active sites in preparations of red blood cells, the figures obtained here are held to reflect more properly the anticholinesterase potency of these agents. Compounds 3113 CT and 3152 CT inactivate red cell cholinesterase more slowly, and are removed less readily by washing procedures, than neostigmine and a parent compound (2842 CT) containing no carbamate groups.