FILM-FORMING POLYMERS FOR COLONIC DRUG-DELIVERY .1. SYNTHESIS AND PHYSICAL AND CHEMICAL-PROPERTIES OF METHYL-DERIVATIVES OF EUDRAGIT-S

Several methylated derivatives of Eudragit S with different degrees of substitution were prepared for evaluation as potential coatings for colon delivery. Water vapor transmission, in vitro dissolution and stability in function of pH were investigated using the technique of isolated films. The data presented demonstrate relative differences in physico-chemical characteristics due to differences in degree of substitution. The relationship of degree of substitution and dissolution pH is direct and inverse for moisture diffusion rate. In the second part of the in vitro study the coating properties of the methyl substitutes of Eudragit S were investigated after application on hard gelatin capsules. The disintegration time of the coated capsules and the release of caffeine at pH 7.5 were in very good agreement with the results obtained with isolated films.