A rapid and sensitive LC-MS/MS method for analysis of iguratimod in human plasma: Application to a pharmacokinetic study in Chinese healthy volunteers.

A rapid, sensitive and reproducible LC-MS/MS method was developed and validated to determine iguratimod in human plasma. Sample preparation was achieved by protein precipitation with acetonitrile. Chromatographic separation was operated on an Ultimate® XB-C column (2.1 × 50 mm, 3.5 μm, Welch) with a flow rate of 0.400 mL/min, using a gradient elution with acetonitrile and water which contained 2 mm ammonium acetate and 0.1% formic acid as the mobile phase. The detection was performed on a Triple Quad™ 5500 mass spectrometer coupled with an electrospray ionization interface under positive-ion multiple reaction monitoring mode with the transition ion pairs of m/z 375.2 → 347.1 for iguratimod and m/z 244.3 → 185.0 for agomelatine (the internal standard), respectively. The method was linear over the range of 5.00-1500 ng/mL with correlation coefficients ≥0.9978. The accuracy and precision of intra- and inter-day, dilution accuracy, recovery and stability of the method were all within the acceptable limits and no matrix effect or carryover was observed. As a result, the main pharmacokinetic parameters of iguratimod were as follows: C , 1074 ± 373 ng/mL; AUC , 13591 ± 4557 ng h/mL; AUC , 13,712 ± 4613 ng h/mL; T , 3.29 ± 1.23 h; and t , 8.89 ± 1.23 h.