Polymeric films intended for a multiple-unit colon delivery system : preparation and characterization

Purpose. Insoluble films with adequate permeability and mechanical characteristics were proposed for the preparation of a previously described time-dependent oral colon delivery device (ChronotopicTM) in a multiple-unit configuration. Indeed, the effectiveness of the functional hydroxypropyl methylcellulose (HPMC) coating of the above-mentioned system was expected to be improved by the application of such films, which would thus allow the relevant thickness to be reduced. Methods. Eudragit®NE coatings with differing amounts (0, 10, 15 and 20% w/w on dry polymer) of a superdisintegrant (sodium starch glycolate, Explotab®V17), were prepared by spraying and cured at 40°C for 24 h. The free films were checked for permeability (modified diffusion cell, deionized water, 37±0.5°C, paracetamol, UV detection 248 nm) and water uptake (oscillating bath, deionized water, 37±1°C) as well as tensile properties (texture analyzer, cross-head speed=500 mm/min, n=5) both in the dry and hydrated state (deionized water, 37±0.5°C, 7 h). Results. The permeability and water uptake of films increased as a function of their % amount of Explotab®V17, as expected in view of the typical behavior of this excipient upon hydration. Generally higher elastic modulus (EM) and lower tensile strength (TS) were brought about by the inclusion of Explotab®V17 in Eudragit®NE films, probably due to the brittle-inducing effect exerted by the superdisintegrant particles. When in contact with the aqueous media, however, the Eudragit®NE/Explotab®V17 films underwent a slight decrease in EM and TS values, reasonably because water would act as a plasticizer. It could therefore be assumed that such films would enable the expansion of the HPMC coating of the ChronotopicTM system thus failing to impact on the relevant release-controlling performance based on swelling/erosion processes. Conclusion. On account of the relevant permeability, water uptake and mechanical characteristics, the Eudragit®NE/Explotab®V17 films under investigation might be adopted to improve the performance of the swellable/erodible HPMC layer of the above described colon delivery system, thereby enabling its preparation as a multiple-unit dosage form.