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The swelling and dissolution behavior of pharmaceutical systems containing a drug and a polymer can be analyzed by a mathematical model which predicts the drug released and the gel layer thickness as a function of time. It is possible to approximate the values of several of the physicochemical parameters of this model in order to obtain an order-of-magnitude analysis of the tablet dissolution process. Selected experimental results of tablet dissolution and drug release are analyzed and conclusions are made about the importance of the drug and polymer content and solubility in the release behavior.

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A model is developed to express the solute diffusion coefficient through semicrystalline polymeric networks. The crystallites create impermeable diffusional barriers around the amorphous regions. Solute diffusion is determined by applying a transport model to the amorphous phase and incorporating the crosslinked polymer structure characteristics. This model is tested with theophylline and vitamin B12 permeation experiments through semicrystalline poly(vinyl alcohol) membranes prepared by annealing of amorphous PVA membranes. The degree of crystallinity varies between 23.1% and 40.5 % on a dry basis. The solute diffusion coefficients correlate well with various parameters of the model.

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