Effect of temperature on drug release and drug absorption in mixed type diclofenac sodium suppositories

New types of diclofenac sodium suppositories known to control a drug release function for hospital preparations were developed based on a concept of the drug delivery system. Hard fat (Witepsol((R))) used asa base of the suppository consists of a mixture of triglycerides, diglycerides and monoglycerides, and each Witepsol((R)) is characterized by its physicochemical properties. Authors disclosed that the amount of drug release measured in the commercially available diclofenac sodium suppositories decreased at a low temperature (36 degrees C). Mixed types of diclofenac sodium suppositories consisting of Witepsol W35((R)) and Witepsol E85((R)) as a base were also prepared and their drug release functions investigated in vitro and in vivo. The in vitro drug release properties changed with the mixing ratios of the two bases and with the temperature of the fluid tested. The amount of released diclofenac sodium increased with increases of both the ratio of Witepsol W35((R)) in the suppository and the temperature of the test fluid. Moreover, several processes causing these phenomena were evidenced by the image analysis. The in vivo absorption of diclofenac sodium was found to be also influenced by these factors. Consequently, it is predicted that such factors as the ratio of Witepsol W35((R)) in the suppository and the temperature will influence the drug absorption and the pharmacological effect of diclofenac sodium suppositories.