Oral mucosal bioadhesive tablets of pectin and HPMC: in vitro and in vivo evaluation

The potential of tablets containing 1:4, 1:1 and 4:1 weight ratios of pectin and hydroxypropyl methylcellulose (HPMC) for the sustained release of diltiazem by sublingual administration has been investigated. Measurements of maximum adhesive force to rat peritoneal membrane indicated a satisfactory bioadhesive strength. An in vitro sustained release of diltiazem over 5 h was achieved with bilayer tablets composed of a drug-free ethylcellulose layer in addition to the pectin/HPMC layer containing drug. Plasma concentration-time curves obtained following sublingual administration to rabbits of single and bilayer tablets with 1:1 weight ratios of pectin and HPMC showed evidence of sustained release of diltiazem. Bioavailability of diltiazem was 2.5 times that achieved by oral administration for single layer tablets and 1.8 times for the bilayered tablets.