Biopharmaceutical study of the hepato-biliary transport of drugs. VII. Improvement of the bioavailability of rifampicin by dosage form design.

Abstract
Improvement of the bioavailability of rifampicin (RFP) was attempted by dosage form design. As lipid vehicles, sesame oil, soybean oil, oleic acid and middle chain triglyceride (MCT) such as tricapriline, were employed. When sesame oil or MCT was used as a lipid vehicle, the percentage recovery of RFP into rat bile was significantly decreased and rat serum RFP level was increased. This improvement of the bioavailability of RFP was also occurred in a dog. The mechanism by which the bioavailability of RFP was improved by lipid vehicles was studied and it has been revealed that this improvement of the bioavailability of RFP is not due to its depressed hepatic uptake from the blood stream after absorption from the gastrointestinal tract but due to the depressed active biliary excretion from the hepatocytes into the bile.