An effective LC–MS method for the simultaneous determination of a potential anti‐rheumatoid arthritis drug, carboxyamidotriazole, and its major metabolite in rat plasma.

Carboxyamidotriazole (CAI) was previously recognized as a well‐tolerated anticancer drug. It has also demonstrated significant anti‐inflammatory effects in various cell and animal model experiments, prompting its investigation as a potential treatment for rheumatoid arthritis. In this study, the potential biotransformation metabolites of CAI were identified both in vitro and in vivo. A sensitive, specific, and accurate LC–MS method was developed for the quantitative analysis of CAI and its major metabolite, CAI‐OH, in rat plasma. CAI, CAI‐OH, and telmisartan (used as an internal standard) were separated using a Zorbax SB C18 column. The mobile phase consisted of water (phase A, containing 0.1% formic acid) and acetonitrile (phase B, containing 0.1% formic acid) at a flow rate of 0.2 mL/min. The analytes were examined using a high‐resolution mass spectrometer, with detected mass‐to‐charge ratios of m/z 424.01293 for CAI, m/z 440.00785 for CAI‐OH, and m/z 515.24415 for telmisartan. Good linearity was observed within the range of 10–5000 ng/mL. Both inter‐ and intra‐batch precision (relative standard deviation, %) were below 6%, and the accuracy ranged from 94.9% to 106.1%. The analytes remained stable throughout the entire experimental period. This method was successfully applied in a pharmacokinetic study of CAI following oral administration in rats. [ABSTRACT FROM AUTHOR]