Fenproporex

Fenproporex is an orally active stimulant drug, which was developed in the 1960s. It is used as an appetite suppressant and a treatment for obesity. It is listed as an illicit substance in many countries due to addiction issues and listed as a prohibited substance by the World Anti-Doping Agency. Structurally, fenproporex (N-2-cyanoethylamphetamine) falls within the phenylethamine and amphetamine chemical class of drugs. The N-2-cyanoethyl substituent was once believed to be resistant to cleavage, because fenproporex -- once recommended as an obesity treatment for patients with cardiovascular disease -- was originally claimed to lack stimulant properties. Contrary to the claim, research has demonstrated easy in vivo cleavage of the N-2-cyanothyl substituent to yield amphetamine as a metabolite. 5 However, in clinical practice, central nervous system stimulative effects are less notorious than with some other agents such as diethylpropion and mazindol. 7

In the United States fenproporex was never approved by the FDA for clinical use due to a lack of efficacy and safety data, and is listed as a drug in Schedule IV of the Controlled Substances Act. In 2006 and 2009, the FDA issued warnings that it had been detected in diet pills sold online, and imported from foreign manufacturers.

Despite being banned in the United States, fenproporex has been described as the second most commonly consumed appetite suppressant worldwide, 6 with fenproporex containing anorectics still being commonly prescribed in South America. Little is known about the specific hazards of amphetamine based diet pills, however case reports have noted side effects such as chest pain, palpitations, headaches, and insomnia. In addition, placebo controlled studies have shown that participants using fenproporex experience more joint pain, sweating, blurred vision and tremor. 2