Emoxypine as a Potential Marker for Identifying Possible Cases of Unintended Meldonium Doping in Sports

In recent years, a scenario involving milk contamination by biotransformation products of the veterinary drug Emidonol has received widespread publicity. Emidonol is intended for use in cattle under pathological conditions accompanied by hypoxia. The drug dissociates into two antihypoxants-meldonium, a metabolic modulator prohibited in sports, and emoxypine, which also has antioxidant properties. A small-scale pilot study involved three volunteers consuming a single 900-mL dose of unpasteurized cow's milk collected on the last (15th) day of treatment with the drug. The mean estimated urinary concentration of emoxypine peaked between 7- and 8.5-h postadministration (1360 ± 240 ng/mL), elimination time being approximately 50-54 h. The mean estimated urinary concentration of meldonium peaked between 5.8- and 9.0-h postadministration and was 322 ± 68 ng/mL, elimination time being approximately 35-45 h. The simultaneous presence of emoxypine and meldonium in urine samples may be indicative of the consumption of Emidonol-contaminated milk, which may facilitate the identification of cases of unintended doping in sport.