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concentrations of omeprazole have not been established for ESGD or EGGD. It is difficult to establish therapeutic concentrations of omeprazole in the blood given oral formulation data due to the large variation in bioavailability resulting in a large range of Cmax concentrations following daily oral dosing (Di Salvo et al., 2016). Following LAO-USA dosing, omeprazole concentrations remained above 4.3 ng/ mL for the seven-day duration of the LAO-USA product. More pharmacokinetic investigation with LAO formulations is necessary to further characterise therapeutic concentrations and may be useful in determining if different doses or dose intervals may achieve greater clinical efficacy. In conclusion, long-acting intramuscular omeprazole
formulations provide convenience in dosing with the potential to improve owner compliance in the medical management of EGUS. Because these formulations bypass the stomach, they may avoid the variation in bioavailability seen with daily dosing or oral formulations. This study provides preliminary safety and efficacy data for the novel LAO-USA formulation. Local injection site reactions were seen following dosing with the LAO-USA formulation, but no systemic side effects were noted. ESGD scores improved by at least one grade following two doses with LAO-USA and are reportedly lower than healing rates of ESGD and EGGD with other LAO formulations. The findings of the study provide preliminary data to support further research with regard to this formulation for FDA approval.
Limitations
A major limitation to the current study is the LAO-USA formulation has not completed FDA investigation or approval, which may increase formulation variability as it is produced or stored. This study did not have positive nor negative control groups which limit interpretation of data. The clinical efficacy results are reported as individual observations over time, and it is recognised that no comparison can be made without either positive or negative control groups. Another limitation recognised in this study is that the gastroscopy evaluator was not blinded to the evaluated subject and that, although a consistent grading system was achieved with a single evaluator, an inherent amount of bias is present in the evaluator being aware of which subject they were scoring. Vaccination on the day of the final injection of the omeprazole could have influenced findings of regional muscle stiffness and pain. The exercise regimens of horses were variable throughout the study and may have confounded bodyweight results.
Authors’ declarations of interest No conflicts of interest have been declared.
Ethical animal research
The experimental protocols of this study were approved by the University Animal Care and Use Committee. (Protocol No. 19-8423).
Owner consent
Written consent was obtained from all animal owners prior to participating in the study.
Source of funding
Funding for this study was provided by BET Pharmacy. They were not involved in study design, data collection and analysis, or in the decision to publish or in manuscript/abstract preparation or approval.
Acknowledgements
The authors would like to thank the CSU Equine Center, CSU Polo Team and individual owners for the use of the horses for the study. We would also like to thank Dr Tom Bergstrom and CSU veterinary students for their assistance with the gastroscopies and blood collection.
Authorship
L. Bass, E. O’Fallon and M. Lehman contributed to study design, data collection, execution and analysis, and manuscript preparation. D. Gustafson contributed to study design, and PK involved in data analysis and manuscript preparation. S. Rao contributed to statistical analysis and manuscript preparation. All authors gave final approval of the manuscript.
References
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