The pharmacokinetics of DWP305, a new combined preparation for hepatic disorders was examined in rats. DWP305 was composed of ursodeoxycholic acid(UDCA), Cardus marianus extract(silymarin 74.5%), fursulthiamine and riboflavin tetrabutyrate(RTB). Especially, this study was focused on the possibilities of drug interaction that the administration of DWP305 may affect the oral absorption of each component. After oral administration of DWP305 and each component drug to rats, the biliary excretion of silybin and tauroursodeoxycholic acid(TUDCA), and the urinary excretion of vitamins were measured by HPLC up to 48 hours. The cumulative amount of TUDCA or silybin in bile was not significantly different between DWP305 and UDCA/silymarin administered groups at doses of 25 and 100 mg/kg. In the case of vitamin study, the urinary thiamine excretion of equivalent molar fursulthiamine administered group was significantly higher than that of thiamine administered group. Urinary riboflavin level of equivalent molar RTB administered group was lower than that of riboflavin administered group, but not significant. These results suggest that the combined preparation may not affect the oral absorption of each component in respect of drug interaction. Also, fursulthiamine and RTB were more effective in oral absorption than thiamine and riboflavin, respectively.