Fenproporex (Perphoxene) (N-2-Cyanoethylamphetamine) (3-(1-phenylpropan-2-ylamino)propanenitrile) (3-[(1-Methyl-2-Phenylethyl)amino]propiononitrile) is a stimulant drug of the phenethylamine and amphetamine chemical classes that was developed in the 1960s.

It is sometimes combined with benzodiazepines, antidepressants, and other compounds to create a version of the "rainbow diet pill".

[7][8][9] Fenproporex has never been approved by the US Food and Drug Administration (FDA) for sale in the US due to lack of efficacy and safety data.

However, in March 2009, the FDA warned consumers that it has been detected as an unlabeled component of diet pills available over the Internet.

[11] Fenproporex is on the list of substances banned by the World Anti-Doping Agency, and any sportsperson testing positive for the substance faces a ban from competition.