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The robustness of controlled release formulations when co-ingested with alcohol is a current concern expressed by regulatory authorities, especially with regard to dose dumping. One such controlled release formulation commonly used is film coating composed of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC). The aim of this study was to investigate how the presence of ethanol in the dissolution medium affects the water permeability of such films. Film samples were prepared in various EC-HPC compositions, and the effect of different ethanol concentrations in the dissolution medium on the permeability was studied using a modified Ussing chamber and tritiated water. It was found that the effect of ethanol on the film permeability varied depending on the composition of the films. The results were interpreted in terms of swelling of the EC in the films, where the swelling increased with increasing ethanol concentration. Thus, for films with low HPC content (non-interconnected pores), the water permeability of the films increased with increasing ethanol concentration as the diffusion through the ethyl cellulose increased due to swelling. However, for films with higher HPC content (having interconnected pores through the films), the permeability decreased, likely due to the swelling of the ethyl cellulose blocking the pores. The interpretation of the results was supported by dynamic mechanic analysis and SEM analysis.

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A water permeability study of ethyl cellulose (EC) film made from an EC-ethanol-water ternary mixture is presented. EC films were prepared by pouring the solution onto a polycarbonate plate and by spraying. The results reveal that the permeability of water, estimated by diffusion experiments, increases as the amount of the nonsolvent increases in the liquid-liquid demixing process. In addition, a relative decrease in the evaporation rate of ethanol compared to that of water following an increase in casting temperature or a higher EC concentration produces a membrane with lower permeability. A mechanical evaluation of the films is also presented. Addition of water to the solvent leads to decreases in the modulus of elasticity, stress, and elongation, due to changes in the morphology of the film. The surface of the film was visualized by SEM photomicrography.