Aminorex is an anorectic stimulant drug. Aminorex inhibits norepinephrine and dopamine transporters. It was briefly available as an appetite suppressant in the 1960s in Switzerland, Germany, and Austria, but was found to cause pronounced vasoconstriction in the pulmonary vasculature, and was withdrawn from the market in 1972 due to several cases of fatal and life-threatening pulmonary hypertension. In the USA aminorex is an illegal schedule I drug.

Aminorex:
https://drugs.ncats.io/drug/2SH16612I9

Aminorex and pulmonary hypertension
There was an epidemic of chronic pulmonary hypertension in Austria, the Federal Republic of Germany and Switzerland, starting in 1967, peaking in 1968/69, and disappearing after 1972. There was a close geographic as well as temporal relation of the epidemic to the marketing and intake of the appetite depressing drug aminorex fumarate (Menocil). 10 years after the epidemic, half of the patients have died, usually of right heart failure. Of those surviving, half present a definite regression of the pulmonary vascular obstruction. Average survival after the initial diagnosis was 3.5 years in those patients who died. Among the surviving patients, the only difference between those with an improved and those with a worsened haemodynamic situation was the age at the beginning of the weight-reducing treatment, those with a progression being 10 years older.

Excerpt from Pub Med:
https://www.ncbi.nlm.nih.gov/pubmed/3928246

Aminorex is a stimulant that was once available in the human market as a weight loss aid. It was pulled from sale in the United States after it was found to cause pulmonary hypertension in people. Regulating aminorex has proven to be a challenge because it is also a metabolite of a legitimate substance. When drugs break down in the body they do so in pieces, and those pieces sometimes happen to be identical to other recognized substances.

Racehorses:
Levamisole, a drug sometimes used to treat equine protozoal myeloencephalitis (EPM), can break down into aminorex in the horse's body, making it appear someone has dosed the horse with aminorex when they didn't. The EDRC has funded research to learn more about the relationship in order to draft guidelines on safe levamisole use.

A horse could have aminorex in its system as a result of having recently eaten hay or grain containing a relative of wintercress. Scollay said there has only been one finding for aminorex in Central Kentucky in the past ten years, even though several wintercress relatives do grow in the area. It seems incidental exposure to the plants in hay isn't causing positive tests

Excerpt from paulickreport.com:
https://www.paulickreport.com/news/the-biz/the-trouble-with-aminorex/

• A weight loss (appetite reducing) stimulant drug
• Developed in 1962
• Introduced as a prescription appetite suppressant in Germany, Switzerland and Austria in 1965
• Withdrawn from the market in 1972 after it was found to cause pulmonary hypertension in approximately 0.2% of patients, and was linked to a number of deaths