Dose related induction of the drug metabolizing enzymes of rat liver by cilobamine.

ABSTRACT

Cilobamine , an antidepressant, was investigated for its influence on the hepatic drug metabolizing enzymes ( DME ) of male Charles River CD rats. Cilobamine doses (3, 10, 30, 100, and 300 mg/kg po, as free base) were compared to sodium phenobarbital (PB) doses (3, 10, 30, 100, and 200 mg/kg po, as free acid). Compounds were given daily for 4 days and all tests were done on Day 5. Ethylmorphine n-demethylase, aniline hydroxylase, microsomal cytochrome P-450 content, relative liver weight, and recoverable microsomal protein were quantitated. The results indicated that cilobamine was an inducer of the DME but not as potent as PB. Cilobamine did not exert any inductive responses at 3 mg/kg. At 10 and 30 mg/kg some but not all test systems were increased. However, at 100 and 300 mg/kg all were increased. PB increased all systems at all doses studied. Electron micrographs of livers of rats given 100 mg/kg of cilobamine or PB revealed hypertrophy of the smooth endoplasmic reticulum. The time course of induction in rats given 100 mg/kg po showed that responses in the cilobamine rats peaked after the second dose and plateaued with later doses. Responses in PB rats increased markedly after one dose and showed a continual increase with later doses. Induction of the DME was also demonstrated in female rats.