Pharmacokinetic and pharmacodynamic effects of two omeprazole formulations on stomach pH and gastric ulcer scores.
Authors: Raidal S L, Andrews F M, Nielsen S G, Trope G
Journal: Equine veterinary journal
Summary
# Editorial Summary Omeprazole remains a cornerstone of gastric ulcer management in horses, yet limited comparative data exist on whether different formulations deliver equivalent clinical efficacy. Raidal and colleagues conducted a masked crossover trial in twelve healthy horses, administering either a novel omeprazole paste (Ulcershield) or a registered reference product across two 6-day treatment periods, whilst measuring gastric pH continuously via indwelling nasogastric probes and assessing plasma pharmacokinetics and gastric ulcer scores. Both formulations significantly elevated gastric pH from baseline (P<0.005) with no meaningful difference between products across median hourly pH, time spent below pH 4, or area under the pH–time curve—findings reinforced by equivalent reductions in ulcer severity scores (P=0.688). Whilst the bioequivalence analysis suggested the novel formulation may achieve slightly higher plasma concentrations, the pharmacodynamic outcomes—the measure that ultimately matters clinically—were indistinguishable between treatments, indicating practitioners can confidently use either product with equivalent expectations for gastric pH control and ulcer healing. The authors appropriately flag that large inter-individual variation in omeprazole absorption and modest sample size limit the precision of their bioequivalence assessment, yet the consistent pH profiles and ulcer responses provide robust reassurance that formulation choice need not compromise therapeutic outcome.
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Practical Takeaways
- •The novel omeprazole paste (ULS) is pharmacodynamically equivalent to the registered reference product and can be used with confidence for managing gastric ulcers in horses
- •Both formulations effectively reduce gastric ulcer severity in clinically healthy horses with consistent pH elevation across a 6-day treatment period
- •Practitioners can choose between the two formulations based on availability, cost, or delivery preference without compromising therapeutic efficacy for gastric ulcer management
Key Findings
- •Both omeprazole formulations significantly increased gastric pH on Day 5 compared to baseline (P<0.005) with no significant difference between products (P=0.773)
- •Both treatments resulted in significantly lower gastric ulcer severity scores (P=0.004 each) with no difference between formulations (P=0.688)
- •The novel ULS formulation matched or slightly exceeded reference product plasma concentrations with pharmacodynamic equivalence demonstrated across all gastric pH parameters measured
- •Equivalent beneficial effects on gastric squamous mucosal ulceration were achieved by both products despite bioavailability variability in the study population