Hepatic and pancreatic metabolism and biliary excretion of the protease inhibitor camostat mesilate.

The hepatic metabolism and biliary and pancreatic excretion of the serine protease inhibitor camostat mesilate and its metabolites FOY-251 and GBA were studied in rats in vivo and in in sutu liver-perfusion experiments. After oral feeding (100 mg/kg) and iv infusion (5 mg/kg.h) of camostat mesilate, the original compound and both metabolites appeared in bile, but could not be detected in pancreatic juice. In plasma, only FOY-251 and GBA were detected. In the perfused rat liver, camostat mesilate (10 microM) was eliminated by 33.8% and its molar rate of degradation to FOY-251 was 25.1%. During the study period about 0.1% of camostat mesilate and FOY-251 appeared in bile. The liver perfusion of FOY-251 or GBA revealed very low hepatic extraction rates of 10.3 and 2.4%, respectively. In conclusion, the low hepatic extraction rate of camostat mesilate and its metabolites leads to high concentrations of the active metabolite FOY-251 in plasma. Camostat mesilate and its metabolites are effectively excreted into bile, but not in rat pancreatic juice.