This stable isotope labeled Snap-N-Shoot^® Reference Solution is suitable for quantification of fenproporex in a variety of LC/MS or GC/MS applications from forensic analysis and urine drug testing and to clinical toxicology and sports testing. Fenproporex, also known as Perphoxene and used as an appetite suppressant for the treatment of obesity, is a stimulant drug of the phenethylamine and amphetamine classes that produces amphetamine as a metabolite. Fenproporex is designated a Schedule IV controlled substance in the US pursuant to the Controlled Substances Act and is also listed as banned substance by the World Anti-Doping Agency.