A validated LC-MS/MS method for simultaneous determination of linagliptin and metformin in spiked human plasma coupled with solid phase extraction: Application to a pharmacokinetic study in healthy volunteers.

Combination therapy has a pivotal role in type II diabetes mellitus management in patients unable to maintain normal glycemic level using metformin alone. Addition of linagliptin, dipeptidyl peptidase-IV inhibitor, to metformin improves glycemic control. This study is concerned with the development of an HPLC-MS/MS method for simultaneous quantification of linagliptin and metformin in spiked human plasma. The method was applied to evaluate the potential pharmacokinetic interactions between the cited drugs in healthy volunteers. Solid phase extraction was applied using Strata™ X cartridge. Separation was carried out on Symmetry® C18 column using methanol: 10 mM ammonium formate buffer (containing 0.2% formic acid) in a ratio of (95: 5, v/v) as mobile phase at flow rate 0.25 mL min-1. Quantification was performed with multiple reaction monitoring in positive ionization mode. The monitored transitions were set at m/z 473.24 → 419.94, 130.14 → 60.18 and 340.27 → 116.07 for linagliptin, metformin and alogliptin (internal standard), respectively. The method was validated according to FDA guidelines. The method showed excellent linearity over concentration ranges 0.25-10 and 25-2000 ng mL-1 for linagliptin and metformin, respectively. The validated HPLC-MS/MS method was successfully applied to pharmacokinetic study of linagliptin and metformin in healthy volunteers after oral administration of Jentadueto® tablets.