In Vitro and In Vivo Evaluation of Combined Time and pH- Dependent Oral Colonic Targeted Prednisolone Microspheres

Aims: to enhance the anti-inflammatory effect as well as oral absorption of prednisolone (PR), through formulation of colonic targeted microspheres prepared from a blend of time and pH- dependent polymers and loaded with PR.
Study Design: In Vitro and In Vivo Evaluation of Combined Time and pH- Dependent Oral Colonic Targeted Prednisolone Microspheres.
Place and Duration of Study: Department of Pharmaceutics and Industrial Pharmacy, Helwan University, Cairo, Egypt between June 2011 and October 2012.
Methodology: Microspheres were prepared by solvent evaporation method using different ethyl cellulose (EC) and Eudragit® S-100 (ES100) ratios with 0.5 and 1% w/v span® 80 as emulsifier. The microspheres were evaluated for surface morphology, particle size, drug encapsulation efficiency % and in vitro drug release at pH 1.2 and 7.4. The anti-inflammatory activity of selected formula was compared to that of conventional PR tablets.
Results: A decrease in drug entrapment efficiency % was obtained with increasing both polymers and surfactant concentrations. Based on drug release results, the formula of 1: 1: 0.16 w/w/w, EC: ES100: PR ratio with 1% w/v span® 80 was selected for further histopathological evaluation of the anti-inflammatory activity in colitis induced-rats. Histopathological study showed undefined tissue necrosis after treatment with the selected microspheres; however, diffused necrosis was observed in rats treated with the commercial tablets. In vivo absorption study showed that values of Cmax and AUC0-24 of both formulations were insignificantly different. However, the occurrence of Cmax of microspheres was significantly delayed in comparison to free drug (9.17 to 2.67hr) (P<.001).
Conclusion: This study has supplied us with brightening results concerning the therapeutic efficacy of a blend of time and pH- dependent polymers colonic targeted microspheres.