Quantitative Determination of Sildenafil (Viagra^®) and Its Metabolite (UK-103,320)in Fluid and Tissue Specimens Obtained from Six Aviation Fatalities*

During the investigation of aviation accidents, postmortem samples from victims are submitted to the Federal Aviation Administration's Civil Aerospace Medical Institute for toxicological analysis. This report presents a rapid and reliable method for the identification and quantitation of sildenafil (Viagra^®) and its active metabolite, UK-103,320. This procedure utilizes sildenafil-d₈ as an internal standard for more accurate and reliable quantitation. The quantitation of sildenafil and UK-103,320 in postmortem fluid and tissue specimens obtained from victims from six separate aviation fatalities is described. The method incorporates solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS-MS) and MS-MS-MS utilizing an atmospheric pressure chemical ionization ion trap MS in the positive chemical ionization mode. Solid-phase extraction provided an efficient sample extraction yielding recoveries ranging from 79 to 88%. The limits of detection for sildenafil and UK-103,320 were 0.39 and 0.19 ng/mL, respectively. The linear dynamic range for both compounds was 0.78–800 ng/mL. The current method proved to be simple, accurate, and robust for the identification and quantitation of sildenafil and UK-103,320 in postmortem fluids and tissues.