Formulation and Evaluation of Bilayered Buccal Adhesive Tablets of Carvedilol

Carvedilol is a non selective α and β receptor blocker which undergoes extensive hepatic first pass metabolism by liver and has poor oral bioavailability of 25% - 30%. In the present investigation Carvedilol was formulated as a bilayered buccal adhesive tablets in order to avoid the firstpass effect and decrease the drug loss using different polymers and excipients. Twelve formulations were made using different concentrations (17%w/w, 35%w/w, 53%w/w) of Carbopol934P, HPMC (3500-6000cps), HPC and Guar gum. The formulations were tested for %weight variation, hardness, Friability, %Drug content, in-vitro drug release, surface pH, Swelling index and Mucoadhesive strength. Mucoadhesive strength was determined by the modified balance method in grams and was found to be between 27.75±0.234gm to 75.94±0.146gm and Surface pH was found to be 7. In-vitro release studies revealed that as polymer concentration increases from 17% to 53%w/w, rate of drug release was retarded and the data was fitted into pharmacokinetic models. Among all other formulations, formulations (F₄,F₈ and F₁₁) containing 17%w/w HPMC, 35%w/wHPC and 35%w/w Guar gum were found to be best as the release was retarded upto 8.5 hours and they have good mucoadhesive strength and they follow zero order with non-fickian diffusion mechanism.