Postmortem tissue samples: an alternative to urine and blood for drug analysis in racehorses.

Although urine is the sample of choice for drug tests in racehorses, it is rarely obtained following the sudden death of a racehorse on the track while racing. The purpose of this study was to demonstrate the significance of postmortem tissue samples as an alternative to urine and blood samples in equine drug analysis following the sudden death of a racehorse on the track while participating in a competitive race. Postmortem tissue samples were frozen (-80 degrees C) until analyzed. A 30-40-g portion of each organ was homogenized in a 0.1 M phosphate buffer (pH 7.4), deproteinized, hydrolyzed with beta-glucuronidase, extracted, and screened by thin-layer chromatography and immunoassay. Samples that initially tested positive for drug(s) were then extracted using high-flow, solid-phase extraction cartridges. The eluates were analyzed by gas chromatography-mass spectrometry. The presence of butorphanol in horses HB355 and CD387, pentobarbital in horse HO940, and ergotamine in horses HO940 and CD387 was detected and confirmed. Thus, in the absence of urine and blood samples following sudden death, postmortem tissue samples are equally useful for forensic toxicological investigations of racehorses.