A rapid and sensitive LC–MS/MS assay to quantify yonkenafil in rat plasma with application to preclinical pharmacokinetics studies

A novel method for the quantitation of yonkenafil, a new synthetic phosphodiesterase V inhibitor, in rat plasma using high-performance liquid chromatography/tandem mass spectrometry (LC–MS/MS) has been developed. The analyte and internal standard (diazepam) were extracted from plasma (100 μl) by liquid–liquid extraction and separated on a C18 column using 10 mM ammonium acetate buffer: methanol (15:85, v/v) as mobile phase in a run time of 3.0 min. The detector was a Q-trap™ mass spectrometer with an ESI interface operating in the multiple reaction monitoring (MRM) mode. The assay was linear over the concentration range 1.0–1000 ng/ml with a limit of detection of 0.20 ng/ml. Intra- and inter-day precision (as relative standard deviation) were both within 8.45% with good accuracy. The method was successfully applied to a preclinical pharmacokinetic study of yonkenafil in rat after sublingual, oral and intravenous administration. The results demonstrate that the sublingual route gives a higher bioavailablity than the oral route and may represent a useful alternative route of yonkenafil administration.