Effects of omeprazole therapy administered via different routes on urinary parameters and selected interleukins in horses with equine gastric ulcer syndrome.

BACKGROUND: Equine gastric ulcer syndrome (EGUS) is commonly treated with proton pump inhibitors such as omeprazole, administered orally or by injection. In humans, omeprazole has been associated with acute interstitial nephritis (AIN) and acute kidney injury (AKI), potentially linked to oxidative stress, and urinary interleukins may serve as early non-invasive markers. However, this association has not been established in horses. OBJECTIVE: To evaluate the effects of oral and injectable omeprazole on basic urinary parameters and selected interleukin levels, with particular emphasis on the potential risk of subclinical AIN. METHODS: A prospective cohort study was conducted in 16 horses diagnosed with EGUS and treated with either injectable or oral omeprazole (4 mg/kg) for 28 days. Urine samples were collected at diagnosis (T0) and after treatment (T1) and analyzed for basic physicochemical parameters as well as interleukin-9 (IL-9), interleukin-18 (IL-18), and tumor necrosis factor alpha (TNF-α). RESULTS: No horses showed clinical signs of renal injury. IL-9 and TNF-α were undetectable, while urinary IL-18 showed no significant group-level changes. At T1, individual IL-18 and GGT values were higher in 9/16 and 7/16 horses, respectively. Urinary sodium concentration increased significantly only in the oral omeprazole group (p = 0.046). CONCLUSION AND CLINICAL IMPORTANCE: The results of this study did not demonstrate an association between omeprazole administration and changes in urinary cytokine concentrations indicative of subclinical AIN in horses. Although no evidence of AKI was observed, these findings should be interpreted with caution and confirmed in larger studies.