Microencapsulation of phenylpropanolamine to achieve sustained release

Phenylpropanolamine HCl was initially microencapsulated with cellulose acetate butyrate, however, the microcapsules did not show acceptable sustained release. A reduction of the drug particle size prior to microencapsulation resulted in a reduction in drug release rate from the microcapsules. The desired drug release profile was attained only when the drug powder was replaced with a drug-resin complex in the microencapsulation process. The pH of the dissolution media had an effect on the drug release profile.