A SENSITIVE LC-MS/MS ASSAY FOR THE DETERMINATION OF NAFTOPIDIL IN HUMAN PLASMA AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

A specific, rapid, and sensitive LC-MS/MS assay was developed and validated for the determination of Naftopidil in human plasma. Naftopidil d7 was used as an internal standard (IS). A faster and one-step protein precipitation (PP) technique was employed for sample preparation. The processed samples were chromatographed on a C-18 column using ammonium formate (5mM) buffer in combination with acetonitrile as the mobile phase. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode, and the protonated ions were monitored at m/z 393 -> 190 transitions for the naftopidil and m/z 400 -> 190 transitions for the IS. The calibration curve was linear over-concentration of 0.30-300 ng/mL, and the method was fully validated as per the recent U.S. FDA Bioanalytical method validation guideline. The precision (%CV) and accuracy results across five concentration levels in 3 different runs were found to be within the specified limits. The present work complied with our initial research objectives and successfully demonstrated the applicability to pharmacokinetic studies.