Simultaneous determination of a new phosphodiesterase-5 inhibitor DA-8159 and its active metabolite in human plasma by high performance liquid chromatography with tandem mass spectrometry

Summary An LC-MS-MS method for the simultaneous determination of DA-8159 and its active metabolite, DA-8164 in human plasma was developed. DA-8159, DA-8164 and the internal standard, sildenafil were extracted from human plasma with dichloromethane at basic pH. A reversephase HPLC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-ammonium formate (10 mM, pH 6.0) (60:40,v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring mode. The method showed a satisfactory sensitivity (lower limits of quantification, 2.0 ng mL¹), precision, accuracy, recovery and selectivity. The successful determination of DA-8159 and DA-8164 in the plasma of a volunteer who ingested a single dose of 100 mg DA-8159 confirms that the present method can be used for plasma analysis for clinical trial.