Studies on Drug Nonequivalence. IX. Relationship between Polymorphism and Rectal Absorption of Indomethacin

Abstract

Absorption of indomethacin from the rabbit rectum was examined in comparison with the suppositories containing indomethacin polymorphs (α- or γ-form). Rectal suppositories were made with Witepsol H₁₂. Plasma levels of α-form indomethacin was higher than that of γ-form. The commercial product (Inteban suppository) made with polyethylene glycol (PEG) base was also examined. Plasma level of Inteban was similar to that of α-form. The relationship between the thermodynamic activities of indomethacin polymorphs and their rectal absorption was discussed.