The influence of formulation on the relative bioavailability of indomethacin suppositories in dogs and rabbits

Abstract The bioavailability of indomethacin in dogs and rabbits after the administration of suppositories of different compositions was determined. The availability of the drug from triglyceride formulations was low but was enhanced after addition of a monoglyceride in both animal models. The absorption enhancing effect was correlated with the monoglyceride fatty acid composition and the in vitro release rate, determined in previous work. With other formulations some striking differences between both animal models were observed. The increase in indomethacin bioavailability from a formulation of a fatty acid-fatty acid methyl ester blend added to triglycerides was only seen in dogs. Two marketed formulations Indocid ® and Dolcidium ® showed a different availability when administered to dogs, and a similar availability when administered in rabbits. A poor correlation between bioavailability and in vitro drug release was found.