Formulation and evaluation of enteric coated HPMC capsule of diclofenac sodium

Enteric coated products are designed to remain intact in the stomach and release the active substance in the upper intestine. Coating of the tablet with the suitable enteric coating material required to disintegrate and release the drug in intestine depending upon the compactness and percent content of additives, while process of coating of hard gelatin capsule lead to shell brittleness and poor adhesion of the coat. Capsules made out of HPMC could be the answer to this to avoid tablet excipients and different processing stages. Rough surface of HPMC capsule facilitated good adhesion for coating enteric polymer. In the present study, capsules were coated with enteric polymer Instacoat super II to the weight gain of 6, 8, 10, and 12%. Dissolution studies demonstrated that enteric coated capsules of coating level 10% were gastric resistant for 2h at pH 1.2 and completely disintegrated in small bowel in an average time of 3h. Capsule made from HPMC resulted in 'good polymer to polymer' adhesion providing gastric integrity and were found stable under accelerated stability studies. Thus HPMC can be considered as a good container for drugs independent of contents in it.