Immunoassay detection of drugs in racing horses: Detection of ethacrynic acid and bumetanide in equine urine by ELISA

Scott D Stanley, T. Wood, J. P. Goodman, P. A. Henry, W. E. Woods, S. L. Chang, H. H. Tai -, D. Watt, S. Kwiatkowski, J. W. Blake, T. Tobin

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


We have raised antibodies and developed one-step enzyme-linked immunosorbent assays (ELISA) for the diuretics ethacrynic acid and bumetanide as part of a panel of pre- and post-race tests for high potency drugs in racing horses. These ELISA tests are rapid (completed within one hour), sensitive, and can be read by eye. The ELISA detects ethacrynic acid at a drug concentration for half-maximal inhibition (I-50) of about 2.5 ng/mL for the parent drug. After dosing horses intravenously with 5 mg ethacrynic acid per horse, the parent drug or its metabolites are detectable in urine for at least 8 hours. The bumetanide ELISA has an I-50 for the parent drug of about 2.0 ng/mL and will detect bumetanide or its metabolites for about 8 hours in urine after intravenous administration of a 1.7-mg dose per horse. Both antibodies are relatively specific for each drug and do not cross-react with other commonly used diuretics or other acidic compounds often found in post- race equine urine samples. Ethacrynic acid and bumetanide are potent diuretics suspected of being illegally substituted for furosemide in certain racing jurisdictions. Development of these rapid, sensitive, and simple tests for these agents will allow more effective pre- and post-race control of the use of these agents in racing horses. Both tests have recently uncovered several 'positives' for these medications in a midwestern racing jurisdiction.

Original languageEnglish (US)
Pages (from-to)95-100
Number of pages6
JournalJournal of Analytical Toxicology
Issue number2
StatePublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry
  • Health, Toxicology and Mutagenesis
  • Toxicology


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