Sustained release formulation of metformin-solid dispersion based on gelucire 50/13- PEG4000: an in vitro study

Metformin is a hydrophilic hypoglycemic agent with permeability and short half-life problems which leads to its low bioavailability. Solid dispersion is one of the unique approaches, to improve bioavailability profiles of drugs. The aim of this study was to prepare and evaluate solid dispersions (SDs) of metformin with polyethylene glycol 4000 (PEG 4000) and Gelucire®50/13 in order to increase its permeability and bioavailability. Solid dispersions of Metformin containing various ratios of PEG 4000: Gelucire®50/13 (1:1, 1:2, 2:1, 1:4, 4:1 as Batch A, Batch B, Batch C, Batch D and Batch E) were prepared using solvent evaporation and fusion techniques. The physical mixtures which served as controls were also prepared. The SDs were evaluated using encapsulation efficiency, percentage yield. The formulations were also characterized with FTIR and DSC. The in vitro drug release studies were also evaluated. The results obtained showed that solid dispersion formulations at pH, 1.2 and 7.4 demonstrated higher release rates than the pure drug. The SDs showed high drug release rates and encapsulation efficiency (% EE) although Batch C containing PEG 4000 and Gelucire 50/13 in the ratio of 2:1 appeared as the batch with most % EE, drug release with broad melting peak. The release rate of metformin increased with increasing amount of PEG 4000. Batch C, SDs containing PEG 4000 and Gelucire 50/13 in the ratio of 2:1 were found to be the most optimized batch with enhanced encapsulation efficiency, most drug release and therefore, improved permeability and bioavailability of metformin.