Report No: DOT/FAA/AM-00/20

Title and Subtitle: A novel method for the determination of sildenafil (Viagra™) and its metabolite in postmortem specimens using LC/MS/MS and LC/MS/MS

Report Date: May 2000

Authors: Lewis, R.J., Johnson, R.D., and Blank, C.L.

Abstract: During the investigation of aviation accidents, postmortem samples from victims are submitted to the FAA's Civil Aerospace Medical Institute for drug analysis. Because new drugs are continually being released to the market, it is our laboratory's responsibility to develop methods which can identify these new drugs. This paper presents a rapid and reliable method for the identification and quantitation of sildenafil (Viagra™) and its metabolite, UK-103,320. Sildenafil, when used properly, is relatively safe. There are, however, certain side effects that could create potential hazards. For example, Sildenafil has been shown to potentiate the hypotensive effects of nitrates commonly employed in the treatment of certain heart conditions.

The procedure described herein incorporates solid-phase extraction and LC/MS/MS and MS/MS/MS utilizing an atmospheric pressure chemical ionization (APCI) ion trap mass spectrometer (MS) in the positive ionization (PCI) mode. Solid-phase extraction provided an efficient sample extraction yielding recoveries of approximately 80%. This method is highly selective and sensitive, having a limit of detection of 1 ng/mL for both compounds. Sildenafil and UK-103,320 were found to have a linear dynamic range of 2-800 ng/mL and 4-800 ng/mL, respectively. This procedure showed intra-day (within day) relative error of equal to or less than 6% and relative standard deviation (RSD) within 4% for both the 50 ng/mL and 200 ng/mL controls. The inter-day (between day) relative errors were equal to or less than 4%, while the RSD was within 12% for both control concentrations. Sildenafil and UK-103,320 were found to be stable in blood for at least one week at 4°C. This method was also used for the determination of sildenafil and UK-103,320 in postmortem fluid and tissue specimens collected from fatal aviation accident victims.

Key Words: Forensic Science, Toxicology, Erectile Dysfunction, Sildenafil, Viagra, LC/MS, LC/MS/MS, LC/MS/MS/MS, Aircraft Accident Investigation

No. of Pages: 15