The potential use of mixed films of pectin, chitosan and HPMC for bimodal drug release

Polyelectrolyte complex (PEC) formation between pectin USP and chitosan was investigated by examining the viscosities of supernatant solutions after removal of the precipitated complex. The amount of pectin, relative to chitosan, required for optimal PEC formation increased as the pH of the solution was reduced. At pH values of less than 1.3, there was no evidence for the formation of the PEG. Swelling studies conducted on pectin/chitosan films, showed minimal swelling occurring when the pectin:chitosan weight ratio was optimal for PEC formation, suggesting the formation of the PEC in situ. The permeability of the films to paracetamol as a model compound was dependent on film composition and was markedly increased after exposure to pectinolytic enzymes, used to mimic conditions in the colon. It may be implied from the results that similar formulations, applied as a film coat to tablets, could be used to achieve bimodal drug release with colonic conditions acting as a trigger for an increased rate of release. (C) 1999 Elsevier Science B.V. All rights reserved.