AN IN-VIVO INVESTIGATION INTO THE SUITABILITY OF PH DEPENDENT POLYMERS FOR COLONIC TARGETING

The behaviour of rapidly disintegrating tablets coated with a model pH dependent polymer, Eudragit S(R), have been investigated in vivo, using gamma scintigraphy, to assess its suitability for use in colonic drug delivery. Studies on human volunteers demonstrated that the polymer is capable of protecting a core tablet through the stomach and upper small intestine. In vivo disintegration was extremely variable in both time (5.0 --> 15 h) and position. The disintegration sites varied from the ileum to the splenic flexure, showing a lack of site specificity. Spreading of disintegrated material occurred aborally with no back mixing of colonic contents being observed. This study gives important information as to the design of an optimum colonic drug delivery system.