Mucoadhesive systems for the buccal release of chlohexidine

Nine mucoadhesive aqueous gels were formulated for the buccal release of chlorexidine (CHX). The mucoadhesive/gel forming agents were carboxymethyl- (CMC), hydroxypropylmethyl- (HPMC) and hydroxypropyl (HPC) cellulose, alone (3% w/w) or in binary mixtures (5% w/w); CHX was present at constant 0.2% concentration in the chemical form of digluconate. Gels were tested for their mucoadhesion using the mucine method at 1, 2 and 3% w/w concentrations. All the samples were examined for the release of the active agent, using a new developed apparatus, able to mimic the environment of the oral cavity and for the coupled release/permeation processes, using a porcine mucosa placed in a Franz cell. The gels release CHX with different rates: when prepared by a single component, practically they release in a comparable mode, even if an order can be shown: CMC > HPMC > HPC. When in mixture these last two polymers enable better control, slowing down the release that range from about 2 h for 3% CMC gel to about 8 h for 2% CMC + 3% HPC gel. All the systems demonstrated suitable to CHX buccal delivery for the prolonged release and reduced transmucosal permeation. The behaviour of the gels was compared with that of tablets, previously studied and containing carbopol 974P and HPMC, alone or in mixture, at different weight concentration. Tablets display a controlled release of CHX only in the presence of carbopol, independently on its concentration, due to electrostatic interaction of the anionic polymer with the cationic drug: the control is of the same order of magnitude as the gels. The two forms can be indicated for different purposes