Efficacy of testing for illegal medication in horses

The efficacy of testing for illegal drugs in race horses was surveyed by evaluating 27 questionnaires received from 28 racing jurisdictions polled. Large variations in the number of samples tested and drugs detected were reported. Some jurisdictions reported only illegal medications, whereas others also reported permitted medications. To facilitate comparison, stimulants, depressants, local anesthetics, narcotic analgesics, and tranquilizers were classified as hard drugs. Other drugs, which are legal in some jurisdictions, were classified as soft. To evaluate the efficacy of testing, positive test results were compared for hard drugs only. Positive test results varied from zero in some jurisdictions for some years to 14.8/1,000 samples tested for one small jurisdiction in one year. The mean rates over the years 1975 to 1983 varied from 0.2 to 6.5/1,000, with a modal positive test result of about 1/1,000. Beside the fact that prerace blood testing is less effective than is postrace urine testing, no cause for these variations in the positive test results could be identified. The positive test results also were compared for jurisdictions with differing medication rules for phenylbutazone (PBZ). Jurisdictions that did not allow PBZ had a mean positive test result for hard drugs of about 1.3 +/- 0.9/1,000 samples tested. Jurisdictions that allowed more liberal use of PBZ had a mean positive test result for hard drugs of about 1.3 +/- 1.0/1,000 samples tested. Seemingly, the presence of PBZ in equine forensic samples did not reduce the ability of forensic laboratories to detect the use of hard or illegal drugs.