Aminorex, an anorectic stimulant was removed from the market in Germany, Switzerland and Austria in the early 1970s due to an association with pulmonary hypertension. It is a Schedule 1 drug in the US and is also a Class 1 banned substance in race horses. In the early 2000s aminorex detected in some race horses established that aminorex is also a metabolite of the immune modulator levamisole. Recent investigation identified a putative plant source for horses failing drug testing with no known exposure to levamisole. What is this plant source?
Barbarea vulgaris, or yellow rocketcress, is a flowering plant that horses may feed on. A recent study demonstrated aminorex by LC/MS in the urine of horses fed Barbarea vulgaris. The putative substance in yellow watercress that is metabolized to aminorex is glucobarbarin. (Maylin G , Fenger C, Machin J, Kudrimoti S, Eisenberg R, Green J, Tobin T. Aminorex identified in horse urine following consumption of Barbarea vulgaris; a preliminary report. Irish Veterinary Journal (2019) 72:15, https://doi.org/10.1186/s13620-019-0153-5; Hess C, Ritke N, Broecker S, Madea B, Musshoff F. Metabolism of levamisole and kinetics of levamisole and aminorex in urine by means of LC-QTOF-HRMS and LC-QqQ-MS. Anal Bioanal Chem 2013;405:4077–4088)
Submitted by Michael Hodgman, MD on behalf of the Herbs and Dietary Supplements Section