The interplay of phase inversion and membrane formation in the drug release characteristics of a membrane-based delivery system

The interplay of phase inversion and membrane formation in the drug release characteristics of a cellulose acetate (CA) membrane-based delivery system has been examined. Drug encapsulated films were cast from solutions of naproxen (drug), CA (polymer), acetone (solvent), and water (nonsolvent). Membrane morphologies, drug release kinetics, and drug–polymer interactions were studied using scanning electron microscopy (SEM), USP apparatus 5 dissolution bath release rate measurements, and differential scanning calorimetry (DSC). The drug load (DL), drug–polymer compatibility, and water content in the casting solution has a significant effect on the membrane morphology and drug release rates. Naproxen was shown to inhibit the locking-in of the phase invertion structure by lowering the glass transition temperature (Tg) of the naproxen/CA membrane. Interestingly, the burst effect for high DL films was avoided for membranes with the honeycomb structure. An interpretation of these results is discussed, and a quantitative model for the drug release mechanism is also given.