The Horse

FEB 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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Page 27 of 51

28 THE HORSE February 2018 can occur at lower doses and with other drugs, especially in horses that appear to be sensitive to NSAIDs' toxic effects. "The key way to avoid NSAID-induced right dorsal colitis is to use NSAIDs at as low a dose as possible for as short a pe- riod of time as possible," Blikslager says. "To reduce the risk of NSAID-induced right dorsal colitis, one consideration is the use of COX-2 inhibitors." Because colonic ulcers result in protein loss, veterinarians can monitor total blood protein to help detect them early. These ulcers can cause clinical signs such as colic with soft manure or diarrhea. "The prognosis for a horse with right dorsal colitis is guarded at best, with sur- vival rates below 50%," warns Blikslager. "To rescue horses from NSAID-induced right dorsal colitis, we use a drug called misoprostol, which is prostaglandin E1," to replenish the prostaglandin the NSAID has inhibited. Kidney damage Horses that are dehy- drated are at increased risk of kidney damage when on NSAIDs. Prostaglandins regulate blood flow to the kidneys similar to how they do to the stomach. And again, we know that NSAIDs reduce pros- taglandin levels, which in this case pares down blood supply to the kidney and results in a lack of oxygen delivery to the tissue, called ischemia. When blood flow decreases significantly, renal papillary ne- crosis might develop—in other words, the kidney tissues die, which severely impairs their function. One sign of this condition is urinating more frequently than normal. Horses that have received high-dose NSAID therapy or were treated while dehydrated (a common clinical sign in colicky horses), for instance, are most at risk for this complication. This is yet another important reason to have your veterinarian manage NSAID treatment. He or she can monitor your horse's renal enzymes and hydration sta- tus to ensure his kidneys are functioning properly while on these medications. When to Use NSAIDs So, when should we reach for these drugs? "Responsible, veterinary-directed use of NSAIDs can be very beneficial and play a huge role in saving a lot of horses' lives," says Fultz. So the first step in using NSAIDs is calling your vet. Veterinarians often prescribe flunixin meglumine for pain associated with the internal organs, including colic and pneumonia. Flunixin meglumine also has anti-endotoxemic properties. Endotoxemia, or bacterial-associated sepsis (infection in the bloodstream), is a condition that occurs when Gram- negative bacteria die in the body and release toxins that can gain access to the systemic circulation via damaged gut lining. This can occur with severe colic lesions, such as intestinal strangulation, as well as with colitis and septic peritoni- tis (bacterial infection of the abdominal lining). Bacterial sepsis causes release of potent inflammatory mediators and pros- taglandins, which most notably results in fever, depression, dehydration, and a high heart rate. Flunixin meglumine has been shown to reduce the adverse cardiovascular effects of these toxins more effectively than other NSAIDs. This so-called anti-endotoxic ef- fect occurs at a lower total dose than the pain-relieving dose. Due to the potential for horses to suffer from sepsis- associated problems when they show signs of colic, veterinarians most commonly use flu- nixin meglumine to treat gastrointestinal pain. Remember, however, that flunixin meglumine is a nonspecific COX inhibitor that impedes both COX-1 gut protection and COX-2 associated with inflammation. NSAIDs: Help or Harm? DRUG NSAID CLASS PRIMARY USES POSSIBLE SIDE EFFECTS Phenylbutazone (Bute) nonselective COX inhibitor Acute muscu- loskeletal pain, such as soft tissue tears, lami- nitis, and bone bruising Jugular vein thrombus, gastric ulcers, right dorsal colitis, kidney damage Flunixin Meglumine (Banamine) nonselective COX inhibitor Pain associated with smooth muscle, including colic and pneu- monia; treating endotoxemia Clostridial myositis if injected intramuscularly (, gastric ulcers, kidney damage, right dorsal colitis Ketoprofen (Ketofen) nonselective COX inhibitor Same as above, with fewer side effects. Recom- mended for horses with sensi- tivity to Bute or Banamine Gastric ulcers, kidney damage Firocoxib (Equioxx) COX-2 selective inhibitor Small intestine colics, osteoar- thritis, chronic laminitis, chronic bone injuries Minimal, though right dorsal colitis cases have occurred

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