Omeprazole use in equine medicine
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Omeprazole Use in Equine Medicine: Treatment and Prevention of Gastric Ulcers
Omeprazole for Equine Gastric Ulcer Syndrome (EGUS) Treatment
Omeprazole is widely recognized as a highly effective treatment for equine gastric ulcer syndrome (EGUS), particularly in performance horses and racehorses, where the prevalence of gastric ulcers is extremely high. Studies have shown that administering omeprazole paste at 4 mg/kg once daily for 28 days results in complete healing of gastric ulcers in 77% of treated horses, with significant improvement in 92% of cases. In contrast, untreated horses rarely show spontaneous healing of ulcers. Continuing omeprazole at either a full or half dose effectively prevents ulcer recurrence, while stopping treatment leads to a return of ulcers to pre-treatment levels .
Dose-Response and Efficacy in Squamous vs. Glandular Ulcers
Research comparing different doses of omeprazole (1, 2, and 4 mg/kg) indicates that lower doses can be as effective as higher doses for healing squamous ulcers, especially when administered before exercise and after a brief fast. However, glandular ulcers respond less favorably to omeprazole, with much lower healing rates compared to squamous ulcers. In some cases, glandular ulcers may even worsen during treatment Sykes2015Sara2023. This pattern is consistent across studies, highlighting the challenge of treating glandular gastric disease with omeprazole .
Injectable Omeprazole: Extended-Release and Long-Acting Formulations
Extended-release injectable omeprazole (ERIO) and long-acting injectable omeprazole (LAIO) have emerged as alternatives to oral formulations, particularly for horses with glandular gastric disease (EGGD). Studies show that ERIO administered at five-day intervals is more effective for healing EGGD than a seven-day interval, while both intervals are similarly effective for squamous disease. Injection site reactions are rare and generally mild . LAIO has been found non-inferior to oral omeprazole, with higher healing rates for EGGD at four weeks (80% for LAIO vs. 42% for oral omeprazole). However, some horses still do not heal after four weeks, and mild, self-limiting injection site reactions can occur Gough2021Lehman2021.
Comparison of Omeprazole Formulations
Different commercial formulations of omeprazole (e.g., enteric-coated granules, buffered pastes) generally show similar pharmacokinetics, and the method of protection (coating vs. buffering) does not significantly affect drug absorption. However, bioequivalence between products is not always established, so direct comparisons should be made cautiously . Studies comparing powder paste and gastro-enteric resistant granules found both to be equally effective for squamous ulcers, but less so for glandular ulcers .
Omeprazole vs. Esomeprazole
Recent research suggests that oral esomeprazole, a related proton pump inhibitor, may be more effective than omeprazole for treating both squamous and glandular gastric disease in horses. Esomeprazole achieved higher healing rates for both types of lesions compared to omeprazole .
Prophylactic Use of Omeprazole in Horses in Training
Meta-analyses confirm that prophylactic omeprazole significantly reduces the occurrence and severity of gastric ulcers in horses undergoing active training. Both 1 mg/kg and 2 mg/kg doses are effective, with a substantial reduction in ulcer prevalence compared to untreated horses .
Safety, Regulation, and Detection
Omeprazole is generally safe, with mild and infrequent injection site reactions reported for injectable formulations. Regulatory studies indicate that omeprazole can be detected in plasma and urine for up to 48 hours after administration, which is important for medication control in racehorses .
Conclusion
Omeprazole is a cornerstone in the management and prevention of equine gastric ulcer syndrome, especially for squamous ulcers. While oral and injectable formulations are both effective, glandular ulcers remain more challenging to treat. Prophylactic use in horses in training is well-supported, and new formulations and related drugs like esomeprazole may offer improved outcomes for some horses. Overall, omeprazole remains a safe and effective option, but treatment should be tailored to the type of ulcer and individual horse response Andrews2010Sykes2015Sundra2023+7 MORE.
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