Rapid LC-ESI-MS-MS Method for the Simultaneous Determination of Clopidogrel and its Carboxylic Acid Metabolite in Human Plasma

A high throughput liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) method is developed for the simultaneous estimation of clopidogrel (SR25990C) and its carboxylic acid metabolite (SR26334) in human plasma using glimepiride as internal standard. The extraction of SR25990C, its metabolite, and IS from the plasma (0.3 mL) involves treatment with phosphoric acid followed by solid-phase extraction (SPE). Sample preparation by this method yields clean extracts with quantitative and consistent mean recoveries of 98.05%, 85.45%, and 105.72% for SR25990C, SR26334, and IS, respectively. The SPE eluate without drying and reconstitution is analyzed by LC-MS-MS, operating in the positive ion and selective reaction monitoring mode. The injection volume is 2 μL with a total chromatographic run time of 5.0 min. The method response is linear over the dynamic range of 0.25 to 25.0 ng/mL for SR25990C and 50.0 to 6000.0 ng/mL for SR26334, with correlation coefficients of r ≥ 0.9989 and 0.9984, respectively. The method is validated to demonstrate its specificity, linearity, accuracy, precision, recovery, matrix effect, dilution integrity, and stability studies. It is applied to study the bioavailability of 75 mg clopidogrel mesylate tablets in 16 human subjects with satisfactory results.