Sustained-release drug delivery system I: Coated ion-exchange resin system for phenylpropanolamine and other drugs.

Ion-exchange resin-drug complexes have been used to formulate sustained-release products of acidic and basic drugs. However, sustained release may be difficult to achieve due to many variables. A novel technique is reported that minimizes these variables by providing a polymeric film coating to the ion-exchange resin-drug complex particles, making drug release from these particles diffusion controlled. Direct application of an atomized polymer solution to the fluidized ion-exchange resin-drug complex particles was ineffective in controlling drug release since the coating came off in the dissolution medium due to swelling and fracturing of the particles. Pretreatment of the ion-exchange resin-drug complex particles with an agent such as polyethylene glycol was essential for the particles to retain their geometry and coating during dissolution. With divinylbenzenesulfonic acid resin complexed with phenylpropanolamine as a model, mixtures of ethylcellulose-coated and uncoated resin-drug complex particles were prepared. These mixtures gave varying drug release profiles that showed rank-order correlation with plasma concentration profiles obtained in bioavailability studies with suspension dosage forms.