Morphine and etorphine: XIV. Detection by ELISA in equine urine

S. Stanley, A. Jeganathan, T. Wood, P. Henry, S. Turner, W. E. Woods, M. Green, H. H. Tai, D. Watt, J. Blake, T. Tobin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We have raised antibodies to morphine and etorphine and developed one-step enzyme-linked immunosorbent assays (ELISA) for these drugs as part of a panel of post race tests for drugs in racing horses. These tests are simple, can be completed in 2 h, and can be read by visual inspection. The morphine ELISA has an I50 for morphine of about 1.5 ng/mL, while the etorphine ELISA has an I50 for etorphine of 250 pg/mL. Cross-reactivity studies show that the antimorphine antibody cross-reacts well with levorphanol, hydromorphone, and oxycodone, while the anti-etorphine antibody showed no cross-reactivity with buprenorphine, diprenorphine, oxymorphone, morphine, or thebaine. The morphine test readily detected parent morphine or its metabolites in equine urine for at least 8 h after administration of 50 mg/horse, while a 0.1 μg/kg dose of etorphine was detectable for up to 48 h post dosing. For each test the background activity in post-race urines was equal to or less than the I50 for the standard curves, making them useful equine forensic tests. Each of these tests has detected 'positives' in post race urine samples and as such these tests are capable of substantially improving the speed and efficacy of both pre-race and post-race testing for morphine, etorphine, and their congeners in racing horses.

Original languageEnglish
Pages (from-to)305-310
Number of pages6
JournalJournal of Analytical Toxicology
Issue number6
StatePublished - 1991

Bibliographical note

Funding Information:
This work was supported by a grant entitled "Immunoassay Test for High Potency Narcotic Analgesics in Racing Horses" from the Kentucky Equine Drug Research Council and the Kentucky State Racing and Harness Racing Commissions. This work was also supported by the American Horse Shows Association and The Horsemens Benevolent and Protection Association.

ASJC Scopus subject areas

  • Analytical Chemistry
  • Environmental Chemistry
  • Toxicology
  • Health, Toxicology and Mutagenesis
  • Chemical Health and Safety


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