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

The effect of a pH-dependent polymer coating, Eudragit S, on its abili ty to protect a model drug and control its release from rapidly disint egrating tablets has been examined in vitro. Conditions were chosen to mimic those likely to occur during transit from the mouth to the colo n. Dissolution was affected by coating thickness and pH. At a given pH , the nature of the buffer system dramatically affected dissolution an d disintegration. Profiling experiments involving pH changes and mimic king the extremes of conditions prevailing in vivo indicated that rele ase of drug may commence in the duodenum or not at all.