Release kinetic study of RHPC coated aspirin microcapsules.

The present communication deals with the study of the effect of pH on the drug release characteristics and the drug release kinetic from the RHPC (Rosin Hard Paraffin Combination) coated aspirin microcapsules. For the purpose of the present study the aspirin microcapsules were prepared by pan coating method imparting 15 coats using 10 per cent RHPC solution in acetone. A standard coating procedure was used to coat the aspirin granules. Dissolution studies were carried out in media with different pH. To get a clear picture drug release studies were conducted in each media for 3 h. The results showed that the RHPC films were resistant to acidic pH releasing less than 5 per cent and 15 per cent drug in 3 h in pH 1.2 and 3.0 respectively. The T 50% in pH 5.0 media was 163 min. The drug was released very quickly in pH 7.2 and 8.0. The release kinetic study showed that the release followed the classical first order pattern though the coated microcapsules used to be intact during the dissolution process, in case of the acidic pH media. The release kinetic was changed when the pH of the dissolution media was 7.2 and above. It was found that during the dissolution process the granules undergo erosion and the release mechanism does not follow a single process.