Effect of ethylcellulose grade and sealant treatments on the production and in vitro release of microencapsulated sodium salicylate.

Sodium salicylate was microencapsulated with ethylcellulose 100 cp by polymer deposition from cyclohexane by temperature change to give a finer product, with slower drug release, than that obtained with 10 cp grade of ethylcellulose. Scanning electron microscope and polymer disc swelling studies confirmed that larger microcapsules after drug release ruptured into smaller particles with swollen surfaces containing pores. Treatment of microcapsules with paraffin wax solution retarded release of core material, the release being affected by the percentage of sealant used and the particle size of the product. The mechanism of release from the sealed microcapsules was complex involving mainly diffusion, but polymer erosion and drug binding were also involved. Other sealant materials were less effective in retarding dissolution.