Pharmacokinetic and pharmacodynamic effects of two omeprazole formulations on stomach pH and gastric ulcer scores.

This study compares the pharmacokinetic and pharmacodynamic effects of a new omeprazole formulation, Ulcershield, and a currently used product, OMO, on stomach pH and gastric ulcer scores in horses. The findings show that both products effectively increased gastric pH and decreased gastric ulcer severity, with potential for the new product to have greater bioavailability.

Research Objective

• The goal of this research was to compare the pharmacokinetic (the actions of drugs in the body over time) and pharmacodynamic (the biochemical and physiological effects of drugs on the body) effects of a new omeprazole formulation called Ulcershield (ULS) against a currently used omeprazole product (OMO).

Methods Used

• The study involved twelve clinically healthy horses over two 6-day treatment periods in a 2 period, 2 treatment crossover experiment.
• The horses were randomly assigned to receive either ULS or OMO.
• Gastric pH was measured continuously for 10 hours on the day before the treatment began and after 6 days of treatment using in situ antimony pH probes within an indwelling nasogastric tube.
• Plasma pharmacokinetics, or drug levels in the bloodstream, were determined on the first and last days of each treatment period.

Results Found

• The treatment significantly increased gastric pH on the sixth day of treatment compared to the day before treatment started, and there was no significant difference between the two products.
• Comparison of median hourly gastric pH, mean gastric pH, the percentage of time with the pH below 4, and the area under the time-gastric pH response curve did not discriminate between the two products.
• Both treatments resulted in significantly lower gastric ulcer severity scores, again with no difference between the treatments.
• Based on the mean log area under the time-plasma concentration curves, it was suggested that the Ulcershield might have a higher bioavailability (the percentage of the drug that enters the systemic circulation) than the reference product, OMO.

Conclusion

• Despite the small sample size, large inter-horse plasma omeprazole concentrations, and low bioavailability of omeprazole affecting the sensitivity of the bioequivalence analysis, the study concluded that Ulcershield matched or slightly exceeded OMO plasma concentrations.
• Moreover, both products resulted in equivalent increases in gastric pH, gastric pH profiles, and a decrease in gastric ulcer scores; as such, they determined that Ulcershield was pharmacodynamically equivalent to OMO.
• The new product Ulcershield was therefore seen as having a comparable beneficial effect on gastric squamous mucosal ulceration.