Formulation and evaluation of Linagliptin coated sustained release tablet of Metformin

The, present study was executed to develop bi-layer tablet containing Linagliptin (LG) (coating material) and metformin (MF) (core material). The hydrophilic HPMC-E5 (for fast release) and HPMC-K100M (for retarded release) polymers were employed for preparation of tablets. Six batches of MR SR tablets were formulated using wet granulation technique, tablets were further coated with LG film. The pre-compression parameters including bulk density, tapped density, angle of repose and hausner ratio were determined for MF. The finished product was characterized for various parameters i.e. weight variation, hardness, thickness, diameter and drug content. Dissolution studies were carried out in paddle apparatus (USP type-II) using acidic and basic conditions. FTIR studies revealed compatibility between drug and polymers. The weight variation, hardness, thickness and diameter were found for all formulations (F-1-F-6). The drug contents for LG were found to be in range of 94.35 +/- 2.88% to 99.33 +/- 2.55% and for MF was 99.12 +/- 0.28% to 99.98 +/- 1.65% for all formulations which met the compendial criteria. The dissolution profile exhibited release of LG for 30 minutes and inner core released the MF for 5 h (F-4), 8 h (F-5) and 10 h (F-6). Based on above data F-6 formulation was considered as optimum one which offered drug release for maximum duration (10 h). The overall results of the study concluded that combination of MF and LG in single tablet using HPMC-E5 and HPKC-K100M polymers could provide immediate delivery of LG and extended release of MF.