Clofibrate microcapsules II: Effect of wall thickness on release characteristics.

The effect of wall thickness on the release characteristics of clofibrate from microcapsules prepared in gelatin-sodium sulfate was investigated. The wall thickness, calculated by recovering the wall material from the microcapsules and using the relationship between two concentric spheres, was related to the surface area of the droplets being encapsulated. Thinner walled microcapsules gave faster release and showed greater deviation from zero-order kinetics but followed the square root of time plots. Microcapsules having thicker walls approximated zero-order release but deviated from the square root of time plots. A theoretical model was developed to explain the release characteristics of the microcapsules. A linear correlation was found between the thickness and the in vitro t50% release time.