Understanding the mechanism for paradoxical effect of ionized and unionized chitosan: Orodispersible tablets of Ondansetron Hydrochloride

The objective of the present investigation was to formulate and evaluate orodispersible tablets (ODTs) of ondansetron HCl possessing sufficient mechanical strength by wet granulation or direct compression method. A combination of glycine and chitosan was employed for providing a sweet tasting disintegrating system. The evaluation of ODTs prepared by a wet granulation method revealed that in vitro disintegration time (DT) as well as wetting time (WT) increased and water absorption ratio (WAR) decreased with an increase in concentration of chitosan (as binder). However, an opposite relationship was obtained when ODTs were prepared by direct compression method. The FTIR spectra and DSC analysis indicated that the -NH3+ moieties of chitosan interacted with COO- moieties of glycine in ODTs prepared by the wet granulation method. However, chitosan was found to be present in the unionized state in ODTs prepared by direct compression method. Furthermore, in vitro as well as in vivo disintegration tests revealed that ODTs containing the chitosan-glycine mixture were superior to those containing well known superdisintegrants. The results suggested that the chitosan-glycine system not only improved disintegration time but also made it possible to prepare ODTs with higher crushing strength as compared to tablets containing superdisintegrants.