PREPARATION AND IN VITRO AND IN VIVO EVALUATION OF BUCCOADHESIVE BILAYERED TABLETS OF DILTIAZEM HYDROCHLORIDE

In this study buccoadhesive bilayered tablets of Diltiazem HCl (DTZ) were prepared in order to improve the bioavailability by the avoidance of hepatic first-pass metabolism, and to prevent frequent administration. Bilayered Tablets containing fixed amount of Diltiazem HCl (DTZ) were prepared by direct compression method using polymers like hydroxyl propyl methyl cellulose (HPMC K4M, HPMC K15M, HPMC K100M) in combination with backing layer of ethyl cellulose and evaluated for physicochemical properties, swelling, bioadhesive strength, in vitro permeation studies, in vitro drug release and possible interaction between ingredients. The physicochemical properties, swelling index, surface pH, bioadhesive strength, in vitro drug release and in vitro permeation studies were found to be dependent on the grade and proportion of buccoadhesive material used. The dissolution of Diltiazem HCl from all the prepared tablets into phosphate buffer (pH 6.8) was controlled for 6 hrs and followed non-Fickian release mechanism. Lower release rates were observed for formulations containing higher concentration of higher viscosity grade of HPMC. FTIR and DSC studies revealed the absence of significant interaction between DTZ and the selected bioadhesive materials. In vivo studies of selected formulation in rabbits demonstrated significant enhancement in bioavailability of DTZ relative to orally administered drug.