Development and validation of a sensitive UPLC-MS/MS method for the simultaneous determination of dapoxetine and its two metabolites in human plasma

• First determination of dapoxetine and its two major metabolites in plasma.
• Only 4.0 min was needed for an analytical run.
• Sample preparation was accomplished by protein precipitation with acetonitrile.

A sensitive and rapid ultra performance liquid chromatography tandem mass spectroscopy (UPLC-MS/MS) method was developed to determine dapoxetine and its two major metabolites (dapoxetine-N-oxide and desmethyldapoxetine) in human plasma simultaneously. After a simple protein precipitation, the analytes and the combined internal standard (carbamazepine) were separated on an Acquity UPLC BEH C18 column using a mobile phase of acetonitrile and 0.1% formic acid in water with gradient elution. Mass spectrometric analysis was performed using a XEVO TQD triple quadruple mass spectrometer coupled with an electro-spray ionization (ESI) source in the positive ion mode. The MRM transitions are of m/z 306.3 → 261.2, m/z 322.2 → 261.2, m/z 292.2 → 261.2 and m/z 237.1 → 194.2 for dapoxetine, dapoxetine-N-oxide, desmethyldapoxetine and IS, respectively. The linearity of this method was found to be within the concentration range of 1.0–200 ng/mL for dapoxetine; 0.5–100 ng/mL for dapoxetine-N-oxide; and 0.1–5.0 ng/mL for desmethyldapoxetine in human plasma, respectively. Only 4.0 min was needed for an analytical run. Intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all of the concentrations. This assay was successfully used to support a clinical pharmacokinetic study following oral administration of dapoxetine tablets in healthy Chinese subjects.

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