Prasad Y V, Krishnaiah Y S, Satyanarayana S
Department of Pharmaceutical Sciences, Andhra University, India.
J Control Release. 1998 Feb 12;51(2-3):281-7. doi: 10.1016/s0168-3659(97)00181-8.
A novel tablet formulation for oral administration using guar gum as the carrier and indomethacin as a model drug has been investigated for colon-specific drug delivery using in vitro methods. Drug release studies under conditions mimicking mouth to colon transit have shown that guar gum protects the drug from being released completely in the physiological environment of stomach and small intestine. Studies in pH 6.8 phosphate buffered saline (PBS) containing rat caecal contents have demonstrated the susceptibility of guar gum to the colonic bacterial enzyme action with consequent drug release. The pre-treatment of rats orally with 1 ml of 2% w/v aqueous dispersion of guar gum for 3 days induced enzymes specifically acting on guar gum thereby increasing drug release. A further increase in drug release was observed with rat caecal contents obtained after 7 days of pre-treatment. The presence of 4% w/v of caecal contents obtained after 3 days and 7 days of enzyme induction showed biphasic drug release curves. The results illustrate the usefulness of guar gum as a potential carrier for colon-specific drug delivery. The study also reveals that the use of 4% w/v of rat caecal contents in PBS, obtained after 7 days of enzyme induction provide the best conditions for in vitro evaluation of guar gum.
一种以瓜尔胶为载体、吲哚美辛为模型药物的新型口服片剂制剂已通过体外方法进行结肠特异性给药研究。在模拟口腔到结肠转运的条件下进行的药物释放研究表明，瓜尔胶可保护药物在胃和小肠的生理环境中不会完全释放。在含有大鼠盲肠内容物的pH 6.8磷酸盐缓冲盐水（PBS）中的研究表明，瓜尔胶对结肠细菌酶的作用敏感，从而导致药物释放。给大鼠口服1 ml 2% w/v瓜尔胶水溶液分散体，连续3天，可诱导特异性作用于瓜尔胶的酶，从而增加药物释放。预处理7天后获得的大鼠盲肠内容物可进一步增加药物释放。酶诱导3天和7天后获得的4% w/v盲肠内容物的存在显示出双相药物释放曲线。结果表明瓜尔胶作为结肠特异性给药的潜在载体是有用的。该研究还表明，在酶诱导7天后获得的PBS中使用4% w/v大鼠盲肠内容物为瓜尔胶的体外评估提供了最佳条件。
