Determination of cilostazol and its active metabolite 3,4-dehydro cilostazol from small plasma volume by UPLC-MS/MS

A simple, rapid and sensitive ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method has been developed for the simultaneous determination of cilostazol and its pharmacologically active metabolite 3,4-dehydro cilostazol in human plasma using deuterated analogs as internal standards (ISs). Plasma samples were prepared using solid phase extraction and chromatographic separation was performed on UPLC BEH C₁₈ (50 mm×2.1 mm, 1.7 µm) column. The method was established over a concentration range of 0.5-1000 ng/mL for cilostazol and 0.5-500 ng/mL for 3,4-dehydro cilostazol. Intra- and inter-batch precision (% CV) and accuracy for the analytes were found within 0.93-1.88 and 98.8-101.7% for cilostazol and 0.91-2.79 and 98.0-102.7% for the metabolite respectively. The assay recovery was within 95-97% for both the analytes and internal standards. The method was successfully applied to support a bioequivalence study of 100 mg cilostazol in 30 healthy subjects.