Simultaneous determination of metformin and vildagliptin in human plasma by a HILIC–MS/MS method

• HILIC–LC–MS/MS for simultaneous determination of metformin and vildagliptin in plasma.
• Quantification of metformin and vildagliptin in plasma for therapeutic drug monitoring.
• A tool for clinical monitoring metformin and vildagliptin.

The objective of this work was to develop and validate a HILIC–MS/MS method for the simultaneous determination of metformin and vildagliptin in human plasma. Chromatographic separation was achieved using an Atlantis HILIC Silica 150-mm × 2.1-mm, 3-μm particle size column maintained at 40 °C. The isocratic mobile phase consisted of 20% water and 80% acetonitrile/water solution 95:5 (v/v), containing both 0.1% formic acid and 3 mM ammonium formate. The flow rate was maintained at 400 μL min−1. Data from validation studies demonstrated that the new method is highly selective, sensitive (limits of detection <1.5 ng mL−1) and free of matrix and residual effects. The new method was also precise (RSD < 9.0%), accurate (RE < 11.2%) and linear (r ≥ 0.99) over the ranges of 5–500 ng mL−1 for each compound. The developed method was successfully applied to determine metformin and vildagliptin in plasma volunteers who orally received a single dose of metformin (850 mg), vildagliptin (50 mg) or drug association (metformin 850 mg + vildagliptin 50 mg). The new method can thus also be used as a tool for the clinical monitoring of metformin and vildagliptin.