Influence of permeability enhancers on the paracellular permeability of metformin hydrochloride and furosemide across Caco-2 cells.

Permeability enhancers can affect absorption of paracellularly transported drugs. This study aims to evaluate effects of permeability enhancers (chitosan, methyl- -cyclodextrin, sodium caprate, sodium lauryl sulfate, etc.) on the permeability of paracellularly absorbed furosemide and metformin hydrochloride. Methyl thiazole tetrazolium bromide test was carried out to determine the drug concentrations in permeability study. Trans-epithelial electrical resistance (TEER) values determined to assess the integrity of tight junctions. Permeability enhancers were applied at different concentrations alone, in dual/triple combinations. Permeability was determined using human colorectal adenocarcinoma (Caco-2) cells (TEER > 400 Ω·cm). Permeability enhancers have no significant effect (<2-fold;  > 0.05) on the permeability of furosemide (1.80 × 10± 4.55 × 10 cm/s); however, metformin permeability (1.36 × 10± 1.25 × 10cm/s) increased significantly ( < 0.05) with 0.3% and 0.5% () chitosan (2.0- and 2.7-fold, respectively), 1% methyl- -cyclodextrin () (3.5-fold), 10 and 20 µmol/L sodium caprate (2.2- and 2.8-fold, respectively), and 0.012% sodium lauryl sulfate () (1.9-fold). Furosemide permeability increased significantly ( < 0.05) with chitosan-sodium lauryl sulfate combination (1.7-fold), and all triple combinations (1.4- to 1.9-fold). Chitosan containing dual/triple combinations resulted in significant increase ( < 0.05) in metformin permeability (1.7 to 2.8-fold). All results indicated that absorption of furosemide and metformin can be improved by the combination of permeability enhancers. Therefore, it can be evaluated for the formulation of development strategies containing furosemide and metformin by the pharmaceutical industry.