Influence of silymarin on drug metabolizing enzymes in rat and man

Male rats weighing 100-130 g were treated orally with a daily dose of 1 X 10 mg Legalon (active principle: silymarin)/100 g b.w. daily for 4 or 10 days. 4 and 10 days after the beginning of the pretreatment a significant increase of the activity of the mixed function oxidation system (Cytochrome P-450, aminopyrine demethylation, p-nitroanisole demethylation) was observed. No alteration of the body weight, the liver wet weight, the microsomal protein content, the cytochrome b5 content and the activities of glucose-6-phosphatase (G-6-Pase) and of a glucoronidase (4-methylumbelliferone) took place after the Legalon treatment. 4 h after the oral administration of 0.5 ml CCl4/kg b.w. the activity of the mixed function oxidation system and of the G-6-Pase was markedly decreased. This effect could not be prevented by the oral administration of 1 X 10 mg Legalon/100 g b.w. 6 h prior to CCl4 application. In human subjects the treatment with daily doses of 3 X 70 mg Legalon during 28 days had no influence on the metabolism of aminopyrine and phenylbutazone. From our results it is concluded that Legalon despite its effects in experimental animals has no influence on drug metabolism in man, when applied in therapeutic amounts.