Effects of barbiturates on the hepatic cytochrome P-450 dependent enzyme system and biliary excretion of exogenous organic anions in rats.

Effect of pretreatment (150 mumol/kg i.p. twice daily for 5 days) wtih six barbiturates (barbital, butobarbital, pentobarbital, amobarbital, phenobarbital and thiopental) on the hepatic microsomal drug methabolizing enzyme system and biliary excretion of bromcresol green and bromsulphthalein-glutathione conjugate has been investigated in rats. All six barburates produced microsomal induction. Phenobarbital, thiopental, barbital and butobarbital increased liver weight, biliary flow and biliary excretion of bromcresol green and bromsulphthalein-glutathione conjugate, however, pentobarbital and amobarbital were ineffective in these parameters. Our results seem to indicate that the enhanced biliary excretion of exogenous anions produced by barbiturates is independent of microsomal enzyme induction.