VALIDATED LC-MS/MS METHOD FOR THE DETERMINATION OF TADALAFIL - A COMPETITIVE PHOSPHODIESTERASE 5 INHIBITOR (PDE5) - FROM HUMAN PLASMA

The purpose of this study was the development and validation of an LC-MS/MS method, for the determination of tadalafil from human plasma. The sample workup involved a simple protein precipitation procedure. A core/shell type analytical column (50x2,1 mm, 2.6 angstrom) was used with C18 stationary phase. The mobile phase consisting of 30% acetonitril and 70% water provided good peak shape, accuracy and precision (stable ionization). The mass spectrometer was operated in positive electrospray ionization mode for analyte and internal standard. The following parameters were evaluated for validation purpose: selectivity, sensitivity, matrix effect, anticoagulant effect, linearity, precision and accuracy, recovery, short and long term analyte/IS stability in solvent/matrix and carryover. The validated calibration range was 22.2-1111.3 ng/ml. The correlation coefficient R-2 was at least 0.9995 in all validation batches. The validated method has been successfully used for the evaluation of bioequivalence of generic tadalafil 20 mg formulations.