[Studies of the metabolism and excretion of silybin in the rat].

The metabolism and excretion of silybin (as N-methyl-glucamine salt) was investigated after intravenous and oral administration to rats. In the urine, silybin was excreted mostly in the unchanged form after intravenous as well as oral application, whilst in the bile it appeared above all in the form of metabolites. By hydrolysis with arylsulfatase/beta-glucuronidase, the metabolites were identified as sulfate and glucuronide conjugates of silybin and dehyrosilybin; the latter appeared in small quantities as a dehydrated product of silybin. After intravenous injection of 20 mg silybin per kg body weight, the excreted amount of silybin after 48 h was 8%, whereas 76% was eliminated in the bile within the same period of time. After oral application of 2--20 mg silybin/kg body weight 20% after 40 mg/kg 35% and after 120 mg/kg 20% of the administered silybin was excreted in the bile during 48 h. The maximum excretion rate was achieved at application of 20 mg/kg p.o. after 1 h. At this dosage, 2--5% was eliminated within the same time in the urine. The excretion of silybin mainly took place (more than 80% of the total of excreted bilybin) in the bile, both after oral and intravenous administration.