Formulation and Evaluation of Buccal Mucoadhesive Bilayered Tablets of Enalapril Maleate

Abstract

The buccal mucoadhesive bilayered tablets of Enalapril Maleate were fabricated with objective of avoiding first pass metabolism and prolonging the duration of action. The tablets were prepared by wet granulation wherein, one layer comprised of drug and bio adhesive polymer, whereas second layer consisted of drug free backing layer of ethyl cellulose. Bioadhesive polymers like Carbopol 934P and one either of three HPMC K4M/ HPMC K15M/ HPMC K100M were employed in combination. A backing layer of ethyl cellulose was provided to ensure unidirectional drug release. FTIR and DSC studies indicated absences of drug-excipient incompatibilities. The tablets were evaluated for physical parameters, surface pH, swelling index, assay, bio adhesion strength, ex vivo permeation studies and in vitro release studies. All the batches showed good bio adhesive force in the range of 0.168 to 0.334 N. A direct correlation was found between the concentration of the bio adhesive polymer and the mucoadhesive strength, where as an inverse correlation was found between concentration of polymer and drug release. In order to determine the mode of release, the data was subjected to zero order, first order, Higuchi and Peppas diffusion models. The formulations F4 (containing 30mg each of  HPMC K4M and Carbopol 934P) exhibited in vitro drug release of 101.0% upto 12 h along with satisfactory bio adhesive force 0.31N. Accelerated stability studies (40±20C/75±5% RH for 3 months) of the optimized formulation (F4) showed absence of any significant changes in hardness, drug content, surface pH, bio adhesive force and in-vitro drug release studies as compared to initial values.

Keywords: Mucoadhesive bilayer tablet, Enalapril Maleate, Carbopol 934P, HPMC, Bioadhesive strength