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A new type of a pH-independent controlled release tablet

1991; Elsevier BV; Volume: 68; Issue: 1-3 Linguagem: Inglês

10.1016/0378-5173(91)90147-g

1873-3476

Naonori Kohri, Yatabe Hiroshi, Ken Iseki, Katsumi Miyazaki,

Pharmaceutical studies and practices

The release of weakly basic drug such as papaverine HCl from sustained-release formulations is dependent on the environmental pH in the gastrointestinal fluid. Precipitation of the poorly soluble free base occurs within the formulation in the intestinal fluid. Precipitated drug is no longer capable of release from the formulation. pH-independent release tablet was prepared by compressing the mixture of papaverine HCl, polyvinyl pyrrolidone (PVP) and citric acid followed by coating the lateral site of the tablet with ethylcellulose. The tablet was shaped into a cylindrical type. When the composition ratio of citric acid to drug was more than about 3.5, the tablet showed a pH-independent release. The percentage of drug release was not influenced by the drug content when the composition ratio of the matrix remained constant. Release rate was controlled by a surface area which could release the drug, and the amount of citric acid or PVP-K 30 incorporated into the matrix. Release rate can be altered freely while maintaining the pH-independent release characteristic by combining the different composition matrices. By simulating these results, drug released as a function of time has been calculated, giving results in good agreement with experiments.