Chromatographic separation and sensitive determination of teriflunomide, an active metabolite of leflunomide in human plasma by liquid chromatography-tandem mass spectrometry.

A sensitive, selective and high throughput liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS) method has been developed for the determination of teriflunomide, an active metabolite of leflunomide in human plasma. Plasma samples were prepared by liquid-liquid extraction of teriflunomide and valsartan as internal standard (IS) in ethyl acetate from 200microL human plasma. The chromatographic separation was achieved on an Inertsil ODS-3 C18 (50mmx4.6mm, 3microm) analytical column using isocratic mobile phase, consisting of 20mM ammonium acetate-methanol (25:75, v/v), at a flow-rate of 0.8mL/min. The precursor-->product ion transition for teriflunomide (m/z 269.0-->82.0) and IS (m/z 434.1-->350.3) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and negative ion mode. The method was validated over a wide dynamic concentration range of 10.1-4001ng/mL. Matrix effect was assessed by post-column infusion experiment and the mean process efficiency were 91.7% and 88.2% for teriflunomide and IS respectively. The method was rugged and rapid with a total run time of 2.0min and is applied to a bioequivalence study of 20mg leflunomide (test and reference) tablet formulation in 12 healthy Indian male subjects under fasting condition. Copyright 2010 Elsevier B.V. All rights reserved.