Non‐steroidal anti‐inflammatory drugs (NSAID e.g. phenylbutazone, “bute”) are commonly used for treatment of inflammation, fever and pain in horses. Adverse effects of these drugs include kidney damage and ulceration of the gastrointestinal tract, primarily the glandular gastric mucosa and right dorsal colon. As stopping NSAID administration may not always be desirable despite development of GI adverse events, other strategies to prevent or treat these complications have sometimes been used e.g. coadministration of acid suppressants such as omeprazole. A recent study sought to investigate if this combined therapy prevents phenylbutazone‐induced equine glandular ulceration1.
Twenty‐two horses with glandular and squamous ulcer scores ≤2 were included in the study. Horses were assigned to treatment groups: phenylbutazone (4.4 mg/kg twice a day by mouth; PBZ), phenylbutazone plus omeprazole (4 mg/kg once daily by mouth; PBZ/OME) or placebo (CON) in a randomized block design based upon initial glandular ulcer score. Horses were treated for up to 14 days. Gastroscopy was performed weekly and hematology and biochemistry performed at Day 0 and study end. Horses were monitored for signs of colic and/or diarrhea.
Glandular ulcer score increased significantly in the PBZ group compared to PBZ/OME group (P = 0.05). More PBZ/OME horses (6/8) had intestinal complications compared to the control group (0/6) (P = .03). These complications included diarrhea (n=1), impaction colic (n=2), unknown colic (n=1) and severe colitis and sepsis requiring euthanasia (n=2). A decrease in plasma protein concentrations (an indication of large intestinal inflammation) was observed in the PBZ group, compared to CON group (P = .03). Five horses were withdrawn from the study due to intestinal complications (3 from the PBZ/OME group and 2 in the PBZ group). One horse in the PBZ group was withdrawn due to severe grade 4 glandular ulcer disease.
Although the number of horses was limited and there was a variable treatment duration among groups due to development of severe complications, coadministration of bute and omeprazole appears to be associated with an increase in intestinal complications. A similar effect has also recently been reported in dogs where combination NSAID and omeprazole therapy increased fecal dysbiosis and intestinal inflammatory markers2. It is unknown what contribution dysbiosis, altered motility and intestinal inflammation play in inducing these intestinal complications. If combination omeprazole and NSAID therapy are necessary, it would seem prudent to additionally administer a gut supplement containing high dose, encapsulated probiotics. Careful monitoring of horses should also be performed receiving combined therapy.
1. Ricord, M, Andrews, FM, Yñiguez, FJM, et al. Impact of concurrent treatment with omeprazole on phenylbutazone-induced equine gastric ulcer syndrome (EGUS). Equine Vet J. 2020; 00: 1– 8. Available HERE
2. Jones, SM, Gaier, A, Enomoto, H, et al. The effect of combined carprofen and omeprazole administration on gastrointestinal permeability and inflammation in dogs. J Vet Intern Med. 2020; 1– 8. Available HERE