The physical properties of polymers used for modified-release coating of pharmaceutical dosage forms are governed by several variables such as plasticization, temperature and humidity. For plasticization, special plasticizers are used that weaken the intermolecular attractions between polymer chains. The addition of plasticizers to a coating formulation generally increases the elongation and flexibility of the coating while reducing the tensile strength and elastic modulus. EUDRAGIT® RS100 and EUDRAGIT® RL 100 polymer films would become brittle without the addition of plasticizers. The present study compares the influence of the plasticizers polyethylene glycol 6000 (PEG) and dibutyl phthalate (DBP) on the flexibility of these coatings. The prepared films were evaluated for clarity, thickness, moisture absorption and mechanical properties and the optimum amount of these plasticizers for coating formulations was determined. Eudragit RS: RL (2:1) and RS: RL (3:1) polymers in coating solution are suitable for controlled release coating of drug loaded pellets with DBP as plasticizer in the range of 1.0% - 2.0% w/v in coating solution.
