Immunoassay detection of drugs in racing horses. III. Detection of morphine in equine blood and urine by a one step ELISA assay.

This study describes the implementation and testing of a one step enzyme-linked immunosorbent assay (ELISA) technique for the detection of morphine in racing horses, indicating its potential usefulness in pre- and post-race narcotic analgesics screening, due to its rapidity, sensitivity, and broad-spectrum reactivity to various opiates.

Introduction and Aim

• The study aims to validate a one step enzyme-linked immunosorbent assay (ELISA) for the detection of morphine and other narcotic analgesics in the blood and urine samples of racing horses.
• This test was evaluated as part of a panel of pre- and post-race tests designed to enhance the efficacy and promptness of drug screenings in the horse racing industry.

Methodology

• The ELISA test was used due to its exceptional sensitivity to morphine having an I-50 value for morphine of about 400 pg/ml, meaning the test can detect extremely low concentrations of morphine.
• The test is also rapid and efficient, where ten samples can be analyzed approximately in thirty minutes.
• Utilizing a spectrophotometer or even just the naked eye, results can be easily read; hence, the test does not require costly or complex equipment.

Results and Discussion

• The ELISA test can detect the presence of morphine or its metabolites in equine blood for up to six hours after administration of sub-therapeutic doses.
• The antibody in the test cross-reacts with other opiate drugs like hydromorphone, orymorphone, nalorphine, levorphanol, and codeine indicating the potential to detect these drugs in blood or urine shortly after administration.
• Introduction of this test into post-race urine screening flagged 18 out of 166 samples as positive for opiates, and further confirmation by mass spectrometry revealed that 13 of these samples were truly positive for opiate presence.

Conclusion

• The results of this study demonstrate that the ELISA test can dramatically improve the speed and efficacy of both pre-race and post-race testing for morphine and other opiates in racing horses.
• The test’s high sensitivity and short run-time make it a robust option to maintain and ensure fair practices in the horseracing industry.