Methadone Screening of Racehorses

Abstract

The misuse of opiates in racehorses relates to their effect of increasing locomotor activity. Because methadone, a narcotic analgesic, has been suspected of use as a doping compound in the past, it was added to the list of banned drugs and should be considered in doping control. Because the literature fails to provide information on detection of methadone in blood or urine of horses, an enzyme-linked immunosorbent assay was developed to monitor this narcotic in equine body fluids. Combined with high-performance liquid chromatography, the immunoassay also served to confirm positives indicated by screening. Following intravenous administration of methadone (0.1 mg/kg), the drug was found for up to 24 h in blood but was never identified in urine (10-pg/mL detection limit). Thus, urine is dismissed as a source of methadone control, and the use of blood to screen racehorses for this narcotic analgesic is suggested.

Multi-drug resistance gene (MDR1) and opioid analgesia in horses

“…DODMAN (1980) observed profound and reliable chemical restraint when methadone in combination with tranquilizers was administrated as a pre-anesthetic in horses. Since 1999, methadone has been included in the list of controlled drugs and should be considered in the doping control, due to the misuse of opiates in racehorses in the past (HAGEDORN et al, 1999). Unfortunately methadone carries a stigma related to its use in opioids addiction programs (WALL & MELZACK, 1999).…”