Pharmacokinetics of silybin following oral administration of silipide in patients with extrahepatic biliary obstruction.

The pharmacokinetics of silybin, the main active component of silymarin, following administration of a lipophilic silybin-phosphatidylcholine complex (silipide) was evaluated in fourteen patients with cholestasis secondary to biliary extrahepatic obstruction. Each patient received a single oral dose of silipide (120 mg, expressed as silybin equivalents). Blood samples for high performance liquid chromatography (HPLC) determination of free (unconjugated) and total (free+conjugated) silybin were collected at frequent intervals for up to 24 h after dosing. Absorption from the gastrointestinal tract occurred rapidly, peak concentrations of free drug being observed within 3 h in most patients. Thereafter, the decline in plasma free silybin levels was relatively rapid, and at 12 h the concentration of free drug had already approached the limit of quantitation (2 ng/ml). At all sampling times, the total (free+conjugated) concentration was much higher than the free concentration. Total silybin levels reached a peak at about 3 to 4 h and persisted at relatively high values (> or = 400 ng/ml) throughout the entire sampling period. On average, the area under the curve for total silybin was more than 40-fold greater than the area under the curve for free silybin. These data suggest that extrahepatic biliary obstruction is associated with a reduced clearance of conjugated silybin, probably due to impaired excretion of the conjugate in bile.