Preformulation studies of mucoadhesive tablets for carbamazepine sublingual administration

The purpose of this research work was the realization of a bi-layered mucoadhesive dosage form intended for carbamazepine sublingual administration and planned in order to obtain a unidirectional drug release and diffusion only across buccal mucosa avoiding the liberation in the buccal environment. Bi-layered tablets were constituted by an impermeable ethyl cellulose backing layer and a mucoadhesive layer. The latter was composed by a blend of a semisynthetic polymer, as hydroxyethyl cellulose or hydroxypropyl methylcellulose, and a synthetic polymer as, Carbopol(®), physically mixed in different ratios. The active ingredient carbamazepine was homogeneously dispersed in the mucoadhesive layer. The prepared formulations were carefully characterized by thickness, friability, swelling index, matrix erosion, ex vivo and in vivo mucoadhesive force and time, moreover patient acceptability was evaluated as well. Tablets constituted by Carbopol(®):hydroxypropyl methylcellulose (25%:75%) and Carbopol(®):hydroxyethyl cellulose (75%:25%) showed the best properties and for this reason were submitted to in vitro release studies. Both tablet groups gave good results in terms of ex vivo and in vivo bioadhesive force and time giving a sustained release.