The in vitro inhibition of the N-demethylation of pethidine by phenelzine (Phenethylhydrazine)

Some properties of the pethidine N-demethylating system of hepatic microsomes are described. The competitive inhibition of this system by phenelzine is also reported. Evidence is given that it is the terminal reaction of the system which is particularly sensitive to phenelzine.Pethidine caused a significant increase in the rate of NADPH oxidation in microsomes from rabbit liver. Some properties of this pethidine—stimulated activity are reported. The pethidine—stimulated activity was inhibited by phenelzine.Microsomal NADPH-cytochrome c reductase activity was only slightly inhibited by phenelzine in amounts which caused complete inhibition of N-demethylation.