Background:
As first-line treatments for diabetes, sitagliptin and metformin have been
widely prescribed as a combination to enhance the therapeutic effect.
Objective:
To establish a methodology to simultaneously monitor the two drugs in vivo by a reversedphase
Liquid Chromatography-Tandem Mass Spectrometric (LC-MS/MS) method.
Methods:
The two drugs were extracted from 50 μl human plasma by ion-pair solid phase extraction.
The separation of the plasma samples was implemented on an Agilent Zorbax SB-CN column (150×4.6
mm, 5.0 µm). The mobile phase was the mixture (80:20, v/v) of methanol and 5.0 mM ammonium formate
in water (pH 4.5). An ion trap spectrometer equipped with an electrospray ionization source was
utilized to detect the elution in positive mode. Quantification of the analytes was achieved by Multiple
Reaction Monitoring (MRM) using the transitions of m/z 408.3→235.1 for sitagliptin and m/z 130.1→
60.2 for metformin.
Results:
Sitagliptin and metformin demonstrated good linearity among the range of 1.00-1000 ng/mL
and 5.00-4000 ng/mL. The intra-day and inter-day investigations displayed precisions of ≤ 3.6% and an
accuracy range of -7.5% to 6.0% for the two drugs. The mean recovery of the two drugs was 96.0% and
98.5%. Under mandatory storage conditions, both the drugs gave an acceptable stability. The throughput
of the assay was found to be more than 100 plasma samples per day ascribed to the run time of 3.0
min for each sample.
Conclusion:
The developed method was successfully applied to a pharmacokinetic study for a fixeddose
tablet formulation containing 50 mg sitagliptin and 500 mg metformin in 12 healthy volunteers.
Application of a Mixed-Mode Solid-Phase Extraction and Cleanup Procedure for LC/MS Determination of Thiabendazole and Carbendazim in Apple Juice