Equine Medicine Resident Massey University Palmerston North, Manawatu-Wanganui, New Zealand
Background: Rebound gastric hyperacidity (RGH) secondary to hypergastrinemia has been suggested to contribute to the rapid recurrence of equine squamous gastric disease (ESGD) following omeprazole discontinuation.
Objectives: To evaluate changes in serum gastrin and chromogranin A (CgA) concentrations in response to medium-term omeprazole treatment and following omeprazole discontinuation.
Animals: Fourteen mature Thoroughbred racehorses in simulated race training.
Methods: Prospective cohort study. All horses received approximately 4 mg/kg of oral omeprazole daily for 61-days, excluding withholding periods where treatment was stopped as part of a concurrent study (57 treatment days). Serum samples were collected on day 0 prior to omeprazole treatment, on day 1 of each week of the treatment period, and for a further five weeks post-discontinuation of treatment. Serum gastrin and CgA concentrations were analyzed using radioimmunoassay and ELISA, respectively.
Results: Median serum gastrin concentrations had a 2.5-fold increase from baseline by day 7 (p< 0.0005) but did not increase further during the treatment period. Median serum gastrin concentrations returned to baseline within 2-4 days after administration of the last dose of omeprazole. No effect of treatment or discontinuation was seen in serum CgA concentrations.
Conclusions and Clinical Importance: Serum gastrin concentrations increased in response to omeprazole treatment but returned to baseline within 2-4 days of the last dose. No effect of treatment or discontinuation was seen on serum CgA concentrations, however accuracy of the CgA results is limited. The findings do not support the use of extended tapering protocols in horses but suggest that management practices targeted at reducing ESGD risk should be optimized in the 2-4 days following discontinuation of omeprazole.
