A selective, sensitive and rapid reversed-phased liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantitation of tadalafil in human blood plasma and seminal plasma. Sample preparation was extracted with methyl tert-butyl ether under alkaline conditions and tadalafil was separated by HPLC using a C18 column and an isocratic mobile phase consisting of methanol and 2 mM ammonium acetate containing 0.05% formic acid in water (52:48, v/v) running at a flow rate of 0.2 mL/min for 5 min. The detection was carried out on a triple-quadrupole tandem mass spectrometer by multiple reactions monitoring (MRM) mode via electrospray ionization (ESI) and domperidone as internal standard. Calibration curves were linear over tadalafil concentration ranges of 2-1000 ng/mL in plasma and 2-100 ng/mL in seminal plasma with the lower limits of quantitation (LLOQ) of 2 ng/mL for both. The intra-day and inter-day accuracy and precision in two matrixes at all QC samples were within the generally accepted criteria for bio-analytical method that precision (RSD) values were below 15% and accuracy (RE) was 1.44-8.32% for plasma and -3.12% to 7.71% for seminal plasma. Finally, the validated method was applicable to clinical pharmacokinetic study of tadalafil in healthy volunteers following oral administration and to further investigate the correlation of tadalafil distribution in human blood plasma and seminal plasma, and tadalafil potential influence in sperm quality.
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