sildenafil-citrate and ammonium-acetate

A simple, sensitive and specific liquid chromatography/tandem mass spectrometry method for the quantitation of aildenafil, a new phosphodiesterase V inhibitor, in human plasma is presented. The analyte and internal standard, sildenafil, were extracted by a one-step liquid-liquid extraction in alkaline conditions and separated on a C(18) column using ammonia:10mM ammonium acetate buffer:methanol (0.1:15:85, v/v/v) as the mobile phase. The detection by an API 4000 triple quadrupole mass spectrometer in multiple-reaction monitoring mode was completed within 2.5 min. The calibration curve exhibited a linear dynamic range of 0.05-100 ng/ml with a 10 pg/ml limit of detection. The intra- and inter-day precisions measured as relative standard deviation were within 8.04% and 5.72%, respectively. This method has been used in a pharmacokinetic study of aildenafil in healthy male volunteers each given an oral administration of one of the three dosages.

Topics: Acetates; Administration, Oral; Ammonia; Area Under Curve; Buffers; Calibration; Chromatography, Liquid; Dose-Response Relationship, Drug; Fasting; Half-Life; Humans; Hydrogen-Ion Concentration; Male; Metabolic Clearance Rate; Methanol; Molecular Structure; Phosphodiesterase Inhibitors; Piperazines; Purines; Reference Standards; Reproducibility of Results; Sensitivity and Specificity; Sildenafil Citrate; Sulfones; Tablets; Tandem Mass Spectrometry; Time Factors