Bute and the Urinary Tract

Q. Can you direct me to any information regarding the effect of phenylbutazone (Bute) on the urinary tract of a gelding, specifically symptoms and prognosis for full recovery?

A. Phenylbutazone works by inhibiting the formation of prostaglandins, the chemical byproducts of inflammation. Prostaglandins appear to have an influence on perfusion (blood flow) into the tissues of the kidney. In certain circumstances, especially when the animal is dehydrated, phenylbutazone might induce a serious disorder called papillary necrosis by inhibiting the formation of prostaglandins. To prevent this problem, caution should be taken not to administer the drug to horses with serious dehydration due to diarrhea, overexertion, or other water depletion situations. If the need is great to reduce inflammation, the treatment should be accompanied by fluid therapy.

There should be no difference between geldings and intact males or females in regard to this problem. Sometimes geldings exhibit discomfort or an unusual posture when urinating, which is almost always due to the buildup of smegma in the opening of the urethra. This buildup is usually referred to as a "bean," which can be remedied by cleaning the penis and urethra carefully.

Often symptoms of tenderness or pain over the back are interpreted as kidney problems. This is almost never the case. When a horse has kidney disease, it has much bigger problems than a sore back.

Like most other medications, phenylbutazone should be used with due regard to complications and side effects. While the kidney damage described occurs only rarely, the occurrence could be disastrous. Always consult with your veterinarian before using any therapeutic agent.

About the Author

A.C. Asbury, DVM

A. C. (Woody) Asbury received his DVM from Michigan State University in 1956, then spent 21 years in California in breeding farm practice and at UC Davis. He joined the faculty at the University of Florida in 1977 and was involved in teaching, research, and administration until 1996. An Emeritus Professor at Florida, he lives in Kentucky, where he and his wife are developing a small farm.

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