The present work was to evaluate the effects of pH sensitive polymers (Eugragit S100 and Shellac) on 5- aminosalicylic acid and prednisolone release from tablets to optimize the coating concentration for colonic delivery. Coating formulation was designed based on the full factorial design. Two indecent variables were used in different concentrations by factorial design. In-vitro dissolution studies, it was found that formulation G4 showed 99.26% of 5-ASA in 18 hours and 99.48% of prednisolone in 24 hours, which lies within the acceptance criteria of 80%. That study conclude that the 1% coating concentration of shellac on inner and 10% coating concentration of Eudragit S100 shows the complete release of drugs to colon for treatment of ulcerative colitis.
