Factors Affecting the Release of Propranolol Hydrochloride from Beads Coated with Aqueous Polymeric Dispersions

Abstract

The main objective of this study was to investigate the release kinetics and mechanism involved in the transport of an ionizable drug through polymeric films applied to drug-loaded beads. The influence of factors such as drug loading and membrane thickness on release kinetics were also investigated. Beads containing propranolol hydrochloride were coated with either of two commercially available aqueous polymeric dispersions, Aquacoat® or Sure lease®, using the Wurster-Process. Analysis of the drug release data suggest that the drug release followed zero-order release kinetics. The plots of drug release constants versus the reciprocal of membrane thickness were found to be linear for both polymeric dispersions. Increasing the osmotic pressure of the dissolution medium was found to decrease the mass of drug released at any given time for both Aquacoat® and Surelease® coated beads. Hence, drug release from these spherical membrane reservoir systems appeared to be diffusion controlled accompanied by osmotic effects. Thickness-corrected, zero-order release rate constants were found to be independent of the drug loading only for the Surelease® coated beads. Scanning electron micrographs (SEM) and examination of drug solubility in urea solutions, were used to confirm and further elucidate the mechanism of drug release. Finally, the effect of storage of coated beads at room temperature on drug release rate was also investigated.