Biphasic drug release: the permeability of films containing pectin, chitosan and HPMC.

The permeabilities of mixed films of pectin/chitosan/HPMC have been studied to assess their value in producing a dosage form with biphasic drug release characteristics. The inclusion of chitosan enhanced the properties of the films, rendering them stable at all physiological pH values. Pectin/HPMC films were soluble at pH values above 3.0. All pectin/chitosan/HPMC films were permeable to a model drug, paracetamol. HPMC initially increased the permeability of the films and subsequently reduced it at higher concentrations. The minimum permeability was obtained at pH 3 and at an HPMC level of 5% where the potential for polyelectrolyte complex formation between pectin and chitosan exists. The permeabilities of the films increased when they were exposed to pectinolytic enzymes, a system designed to mimic conditions in the colon. The film formulation thus show the potential for biphasic delivery with an initial, controllable slow phase that can be manipulated by changes in the formulation followed by a faster phase under conditions pertaining in the colon.