Water vapor sorption of hot-melt extruded hydroxypropyl cellulose films: effect on physico-mechanical properties, release characteristics, and stability

Hot-melt extrusion technology was used to prepare thin polymer films containing hydroxypropyl cellulose and clotrimazole (CT). Films containing hydroxypropyl celluloses of different molecular weight and the drug were investigated for moisture-sorption, mechanical properties, and release characteristics. Stability of the films was also studied at 25 degrees C/60% relative humidity (RH) and 40 degrees C/75% RH for up to 3 months. To study the moisture-sorption of the hot-melt extruded films, a rapid dynamic vapor sorption technique was used. Mechanical properties were evaluated using the Texture Analyzer. The molecular weight of the polymer had a significant effect on the mechanical and release characteristics of the films but did not influence the equilibrium moisture content in the films stored at RHs ranging from 0 to 90%. However, the time to reach equilibrium was longer for the higher molecular weight polymers. The drug release rate was dependent on the rate of erosion, which in turn depended on the molecular weight of the polymer. The films were stable at 25 degrees C/60% RH for up to 3 months with no significant degradation or recrystallization of CT. However, recrystallization of the drug was observed within the films stored in accelerated stability conditions at the end of 3 months in which only 92.9% (+/-1.9) CT remained.