Development and Validation of LC-ESI-MS Method for the Quantification of Dapoxetine in Rat Plasma

A sensitive and simple liquid chromatography/electrospray mass spectrometry (LC-ESI-MS) method for determination of dapoxetine in rat plasma using one-step protein precipitation was developed and validated. After addition of,midazolam as internal standard (IS), protein precipitation by acetonitrile was used in sample preparation. Chromatographically separation was achieved on an SB-C18 (2.1 mm x 150 mm, 5 mu m) column with acetonitrile-0.1% formic acid as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selected ion monitoring (SIM) mode was used to quantification using target fragment ions m/z 306 for dapoxetine and m/z 326 for the IS. Calibration plots were linear over the range of 5-1000 ng/mL for dapoxetine in rat plasma. Lower limit of quantification (LLOQ) for dapoxetine was 5 ng/mL. Mean recovery of dapoxetine from plasma was in the range of 92.4-98.6%. CV of intra-day and inter-day precision were both less than 15%. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of dapoxetine in rat plasma.