Hepatic drug-metabolizing enzyme activity in rats pretreated with (-)-emetine or (plus or minus)-2,3-dehydroemetine.

1. Pretreatment of female rats with (-)-emetine or (+/-)-2,3-dehydroemetine (at 18mumol/kg body wt. for 24h) prolongs the hexobarbital-induced sleeping-time of the treated animals. 2. This effect is not observed on pretreating animals with other compounds closely related to (-)-emetine, such as (-)-isoemetine or (+)-O-methylpsychotrine. 3. Liver microsomal drug-metabolizing enzyme activity in vitro as measured by N-demethylation of aminopyrine and azo-reduction of Neoprontosil is inhibited in rats pretreated with (-)-emetine or with (+/-)-2,3-dehydroemetine. 4. These inhibitory effects on drug metabolism in vitro are not observed in corresponding experiments involving pretreatment of rats with (-)-isoemetine or (+)-O-methylpsychotrine. 5. Co-administration of emetine or 2,3-dehydroemetine and sodium phenobarbital or 1,1-dichloro-2-o-chlorophenyl-2-p-chlorophenylethane to rats abolishes or greatly diminishes the stimulation of drug-metabolizing enzyme activity in vitro usually obtained by the administration of phenobarbital or 1,1-dichloro-2-o-chlorophenyl-2-p-chlorophenylethane alone. 6. Further, in rats pretreated with sodium phenobarbital and subsequently injected with emetine or 2,3-dehydroemetine the pre-stimulated drug-metabolizing enzyme activity in vitro is diminished. 7. The inhibitory effects on drug-metabolizing enzyme activity after pretreatment with (-)-emetine or (+/-)-2,3-dehydroemetine do not appear to be related to NADPH generation.