Pectin (PEC) and ethylcellulose (EC) are widely employed as colon-targeted coating materials due to their complementary properties, namely enzymatic degradability of pectin in the colonic environment and hydrophobicity of ethylcellulose. Beyond polymer selection, processing parameters critically influence the mass transfer characteristics of pharmaceutical coatings. This study investigated the relationship between the permeability of PEC-EC isolated films and drug release profiles of corresponding pellet coatings, prepared at a fixed polymer ratio but varied process conditions for the model drug theophylline. Manufacturing parameters including solid content of the polymer dispersion, film/coating thickness, atomization air pressure, and drying temperature were systematically adjusted. The resulting films and coatings exhibited significant variation in permeability coefficients and drug release rates. Higher dispersion viscosity and solid content, coupled with reduced spraying level, correlated with increased permeability and accelerated drug release. Notably, lower atomization air pressure enhanced film permeability but did not significantly affect drug release from coated pellets within the tested range. The observed discrepancy between sensitivity of the isolated films to changing manufacturing conditions and the robustness of the pellet coating process underscores the reliability of fluidized bed coating processes in achieving consistent drug release kinetics. These findings highlight the consistent influence of process parameters on transport properties and suggest that permeability testing of isolated films may serve as a predictive and cost-effective screening tool for optimizing coating formulations.
Keywords: Aqueous based coating; Diffusion; Drug release; Ethylcellulose; Freestanding film; Pectin; Process parameters.
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