Formulation Development and Evaluation of Bilayer Tablets of Telmisartan for Immediate Release and Metformin Hydrochloride for Sustained Release

The aim of the study was to design bilayer tablets containing Telmisartan for immediate release and Metformin hydrochloride for sustained release. Telmisartan has the strongest binding affinity to AT1 receptor among various ARBs and also has positive effects on insulin resistance syndrome because of the partial agonistic activity towards peroxisome proliferator-activated receptor-gamma (PPARγ). Metformin is an antihyperglycemic not a hypoglycemic. Combinations of both drugs effect the treatment of hypertension in Type-II diabetes mellitus patients and improve the patient compliance. Telmisartan belongs to class II drug in BCS classification. Enhancement of solubility of Telmisartan was observed with physical mixture of drug with beta (β)-Cyclodextrin. Immediate release layers were prepared by wet granulation method using various concentration of sodium starch glycolate as superdisintegrant. SR layers were prepared by wet granulation method using swellable polymer HPMC K4 M and HPMC K100 M in different ratios. Both Immediate (L1, L2 and L3) and Sustained release (F1, F2, F3, F4 and F5) tablets were formulated and evaluated. All the values were found to be satisfactory and were within limits. From the results obtained I3 and S5 were selected and finally compressed into bilayer tablets. In vitro release studies were carried out using USP type II paddle apparatus in 0.1M HCl for first 2 hours and pH 6.8 phosphate buffer solution for next 8 hours as dissolution medium. Stability studies were carried out at 40 ± 2°c and 75±5% RH for a period of three months.