High Performance Liquid Chromatographic Determination of Inactive Carboxylic Acid Metabolite of Clopidogrel in Human Serum: Application to a Bioequivalence Study

A sensitive and rapid method is described for determination of clopidogrel carboxylic acid (CCA), the inactive metabolite of the antiplatelet agent clopidogrel in human serum. The analytical procedure involves liquid-liquid extraction of the analyte and an internal standard (phenytoin) with ethyl acetate. A mobile phase consisting of 0.05 M phosphate buffer containing triethylamine (0.5 ml/l; pH 5.7) and acetonitrile (56:44; v/v) was used and chromatographic separation was achieved using a C18 analytical column at detector wavelength of 220 nm. The calibration curves were linear over a concentration range of 0.05-10 g/ml of CCA in human serum. The total run time of analysis was 5.5 min. and the lower limits of detection (LOD) and quantification (LOQ) were 0.02 and 0.05 g/ml, respectively. The method validation was carried out in terms of specificity, sensitivity, linearity, precision, accuracy and stability. The validated method was applied in a randomized cross-over bioequivalence study of two different clopidogrel preparations in 24 healthy volunteers.