The behaviour of bioadhesive betamethasone tablets in the mouth.

Disk-shaped adhesive tablets, for treatment of mouth lesions, were prepared by direct compression of a mix of high viscosity sodium carboxymethyl-cellulose and 0.061% betamethasone valerate. They were evaluated in six healthy volunteers. The tablets hydrated rapidly, increased their wet weight fourfold in 15 min and maintained contact with the oral mucosa for at least 4 h. Erosion of the tablets was variable with only minor losses in one subject at all times tested, whereas over 80% tablet weight loss occurred in two subjects after 2.5 h. These differences were not solely related to differences in salivary flow. Loss of betamethasone occurred in parallel with the loss of weight from the tablet suggesting that drug release was mainly by erosion of the gelled polymer and not by diffusion from the matrix. The tablets provided prolonged contact with the mucosa but the intersubject variability and drug loss should be addressed to improve the formulation.