[Inhibitory effect of antineoplastic agents on human cholinesterases]

Human motor endplate acetylcholinesterase was inhibited in vitro by alkylating antineoplastic agents, most strongly by mechlorethamine, followed by DTIC, ACNU, cyclophosphamide and ifosfamide. Eleven other antineoplastic agents did not inhibit the enzyme substantially nor interfered with cholinesterase measurement. Cyclophosphamide and mechlorethamine inhibited human plasma pseudocholinesterase most strongly, followed by thiotepa, ACNU, DTIC, ifosfamide and BCNU. Mechlorethamine, ACNU and ifosfamide inhibited the motor endplate and plasma cholinesterase practically equally, DTIC inhibited motor endplate cholinesterase more strongly, while cyclophosphamide was a more selective inhibitor of plasma cholinesterase. Inhibition of human red blood cell acetylcholinesterase was identical to that of motor endplate acetylcholinesterase; therefore, red cells would be a preferable indicator in monitoring cholinesterase inhibition by antineoplastic agents.