Immunoassay detection of drugs in racing horses. VIII. Detection of cocaine in equine blood and urine by particle concentration fluorescence immunoassay

We have developed a Particle Concentration Fluorescence Immunoassay (PCFIA) for cocaine as part of a panel of pre- and post-race tests for illegal drugs in racing horses. This PCFIA test is very sensitive, with an I-50 for cocaine of about 2.5 ng/mL. It does not cross-react significantly with scopolamine, atropine, procaine, or ecgonine. Benzoylecgonine cross-reactivity is less than 10%. The test is rapid, and a normal complement of pre-race tests can be analyzed within one hour. This test detects the presence of cocaine or its metabolites in equine urine for up to 48 hours after a dose of 10 mg/horse, and for at least 72 hours if the dose is 80 mg or larger. In serum, the test detects cocaine for at least 8 hours and likely longer at the 10 mg/horse dosing level. The test is many times more sensitive than thin layer chromatographic tests for cocaine, and is capable of improving the quality of both pre- and post-race testing for cocaine in horses. On initial introduction into post-race urine screening the test flagged 2 of 83 samples 'suspect' for cocaine, which samples subsequently confirmed positive for cocaine by mass spectrometry. Because of the ready availability of cocaine and the small doses (less than 10 mg/horse) that are effective in racing horses, a simple, inexpensive, and sensitive test for cocaine is essential for control of abuse of this drug in racing horses.