A new type of double-layered osmotic pump controlled release tablets of bezafibrate with poor water solubility and large dosage

Abstract

A new type double-layered osmotic pump (DOP) system was developed for the delivery of water insoluble drug bezafibrate with daily dose of 400 mg, polymer was used as drug carrier and alkaline substance was added to the core as solubilizer. This novel DOP was designed as a combination of various osmotic pumps, such as push-pull osmotic pump, elementary osmotic pump and monolithic polymer osmotic pump. Two layers of the osmotic pump system were both drug-containing, the first layer of the DOP was designed using elementary osmotic pump theory which involved 20 mg sodium carbonate to enhance the solubility of model drug, the second layer was designed using monolithic polymer osmotic pump theory by adding 50 mg polyoxyethylene oxide as suspending and swelling agent, and a double layer osmotic pump was formed by the combination of the two layers which could operate as a push-pull osmotic pump. Orifices with the same diameter at 0.8 mm were drilled on both sides of membrane surfaces and the release profile of drug presented zero-order in 12 h. The results showed that factors that had considerable influence on in vitro drug release behavior were: the proportion of bezafibrate in two layers, the amount of polyoxyethylene oxide in core tablets, the percentage of polyethylene glycol in coating materials, the coating level and the orifice.