Re‐evaluation of the regulation of omeprazole in racehorses: An evidence‐based approach

Abstract

Medication control and doping control have been established in horse racing to ensure the integrity of the sport and the welfare of the horses. This ensures that horses do not compete under the influence of any drugs, including omeprazole, a therapeutic medication used to treat equine gastric ulcer syndrome. In this study, pharmacokinetic data were produced in equine plasma and urine following an oral administration of 4 mg/kg of generic buffered formulation of omeprazole to six Thoroughbred horses in five daily doses to determine an appropriate screening limit and detection time in equine plasma and to assess whether the current detection time of 72 hr in equine urine would be applicable when an alternative omeprazole product is administered. C of 436-2,432 ng/ml and AUC of 1,476-4,371 ng hr ml were obtained for plasma and indicated, in conjunction with other published oral omeprazole studies, that an appropriate plasma screening limit would be 500 pg/ml with a detection time of 48 hr. Urine analysis showed that omeprazole could be detected for up to 25 hr above the previously established urine screening limit of 500 pg/ml and thus indicated that the detection time advice could be potentially reduced from 72 to 48 hr to allow more comprehensive treatment of gastric lesions.

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

“…Other studies in horses have addressed the pharmacokinetics, disposition, and detection of the antiulcer drugs cimetidine, ranitidine, and omeprazole in plasma 311,312 and urine 312 ; the vasodilators isoxsuprine 313 and sildenafil 314 in urine and plasma; the antibiotic metronidazole in plasma 315 ; the antitussive dextromethorphan in plasma and urine 316 ; the expectorant guaifenesin in serum 317 ; the mood stabilizer lithium in urine and plasma 318 ; the solvent dimethyl sulfoxide in plasma and urine 319 ; phosphorothioated oligonucleotides in plasma 44 ; and the narcotics fentanyl in urine, 320 hydromorphone in urine, 26 and morphine in hair 38,321 and urine 322 …”

“…Its misuse motivated the development and application of methods for its detection in horse urine 309 and horse plasma. 310 Other studies in horses have addressed the pharmacokinetics, disposition, and detection of the antiulcer drugs cimetidine, ranitidine, and omeprazole in plasma 311,312 and urine 312 ; the vasodilators iso-…”

Pharmacokinetic and pharmacodynamic effects of 2 registered omeprazole preparations and varying dose rates in horses

“…In our study, omeprazole was rapidly eliminated (mean elimination half-life of approximately 60 minutes) after administration of both oral preparations, as has been described previously. 16,25,26,28,29 Omeprazole might display concentration-dependent elimination kinetics, 27 Despite differences in dose rate, both products demonstrated similar beneficial effects on gastric pH and healing of gastric squamous ulcers. The feeding protocol used in the current study was identical to that used previously by this group, 20 The pH of gastric secretion has been determined previously by collection of samples from gastric cannulas, 13,30,31 aspiration of gastric fluid via endoscopy or nasogastric intubation, or indwelling nasogastric pH probes.…”

“…In our study, omeprazole was rapidly eliminated (mean elimination half-life of approximately 60 minutes) after administration of both oral preparations, as has been described previously. 16,25,26,28,29 Omeprazole might display concentration-dependent elimination kinetics, 27 but differences were not consistently observed between NOV and REF, despite the disparate dose rates administered and the greater plasma concentrations observed for NOV. As has been previously reported after IV administration, 28 there was no evidence of drug accumulation with repeated oral administration in the current study. The pH of gastric secretion has been determined previously by collection of samples from gastric cannulas, 13,30,31 aspiration of gastric fluid via endoscopy or nasogastric intubation, or indwelling nasogastric pH probes.…”

The Impact of Two Recommended Withholding Periods for Omeprazole and the Use of a Nutraceutical Supplement on Recurrence of Equine Gastric Ulcer Syndrome in Thoroughbred Racehorses

“…The recommended withholding period (RWP) for omeprazole varies between racing jurisdictions with RWP0 and RWP2 commonly used [21]. To the authors' knowledge, the rate of recurrence of EGUS during these RWPs and following the discontinuation of omeprazole therapy has not been studied.…”