Transmucosal sustained-delivery of chlorpheniramine maleate in rabbits using a novel, natural mucoadhesive gum as an excipient in buccal tablets.

The objective of this study was to evaluate the gum from Hakea gibbosa (Hakea) as a sustained-release and mucoadhesive component in buccal tablets following their application to the buccal mucosa of rabbits. Flat-faced core tablets containing either 22 or 32 mg of Hakea and 40 or 25 mg of chlorpheniramine maleate (CPM) per tablet with either sodium bicarbonate or tartaric acid in a 1:1.5 molar ratio were formulated using a direct compression technique and were coated with Cutina(R) on all but one face. The resulting plasma CPM concentration versus time profiles were determined following buccal application of the tablets in rabbits. The strength of mucoadhesion of the tablets was also quantitated in terms of the force of detachment as a function of time. Following the application of the mucoadhesive buccal tablets, the following values for several pharmacokinetic parameters were obtained. The force of detachment for the mucoadhesive buccal tablets containing 22 mg of Hakea and either 25 and 40 mg CPM, and 32 mg Hakea and 40 mg CPM increased from 1.64+/-0.47 to 7.32+/-0.34 N, 1.67+/-0.30 to 7.21+/-0.36 N, and 2.93+/-0.73 to 7.92+/-0.60 N, respectively from 5 to 90 min following application to excised intestinal mucosa. Addition of either sodium bicarbonate or tartaric acid, as well as higher amounts of CPM, did not affect the mucoadhesive bond strength. These results demonstrate that the novel, natural gum, H. gibbosa, may not only be used to sustain the release of CPM from a unidirectional-release buccal tablet, but also demonstrate that the tablets are sufficiently mucoadhesive for clinical application. The mucoadhesive strength as measured by the force of detachment, can be modulated by altering the amount of Hakea in the tablet. The mucoadhesive buccal tablets evaluated represent an improved transbuccal delivery system for conventional drug substances.