Trepibutone

The release of a drug having low solubility in a certain pH range from controlled-release microspheres using tetraglycerol pentastearate and tetraglycerol monostearate in combination as the matrix base showed pH dependence. Trepibutone, an acidic drug having lower solubility in an acidic medium, was released pH-independently from the microspheres which incorporated magnesium oxide, a solid base. It might have resulted from the pH inside the matrix being kept in an optimum range for drug release due to the incorporation of a solid base. On the other hand, the addition of water soluble acidic or basic excipients was ineffective to achieve pH-independent release. For papaverine, a basic drug, pH-independent drug-release characteristics could be achieved by adding Eudragit L100-55, an enteric polymer. It is thought that the enteric polymer increased the pores for drug release by dissolving in a higher pH range, where the solubility of papaverine is low, and thereby made the release pH-independent. Further, selecting a polyglycerol ester of a fatty acid with an appropriate hydrophile-lipophile balance as the matrix could yield a drug with the desired release rate at any pH.

The spasmolytic action of 3-(2,4,5-triethoxybenzoyl)propionic acid (AA-149) on the biliary tract was investigated in anesthetized dogs. Intravenous administration of AA-149 at 2 mg/kg and higher doses produced a dose-dependent reduction in passage resistance through the choledochoduodenal junction and in gallbladder pressure, and a dose-dependent increase in bile flow. AA-149, like cholecystokinin, decreased biliary ductal pressure in spite of increasing the bile flow in dogs with ligation of the cystic duct of the gallbladder, whereas taurocholate increased the pressure as well as the bile flow. Moreover, the spasmic response of the choledochoduodenal junction to morphine was depressed strongly by AA-149, BUT NOT CONSISTENTLY BY ATROPINE. The effects of AA-149 were not influenced by pretreatment with atropine, phentolamine or propranolol. These findings strongly suggest that AA-149 relaxed the biliary tract and depressed the morphine-induced spasm by a mechanism different from those of anticholinergic and sympathomimetic agents.