Be Aware of Systemic Effects of Topical Steroids

When a horse has a skin problem, most people reach for the steroid creams. However, because the creams are topical, many people don't realize they can have systemic effects on a horse. A recent study showed that a course of topical dexamethasone affects many of the horse's hormones, including insulin, glucose, and triglycerides.

"Skin creams containing glucocorticoids are used for the treatment of skin inflammatory reactions and allergy," said Getu Abraham, DVM, PhD, from the Institute of Pharmacology, Pharmacy, and Toxicology at the Faculty of Veterinary Medicine of Leipzig University in Germany. "In normal horses, the application of a skin cream containing dexamethasone caused systemic adverse reactions even when applied and rubbed on normal skin for a short time. Such reactions can be measured in the blood."

The researchers treated 10 Thoroughbreds twice a day for 10 days with 50 g of dexamethasone ointment, and then took blood and measured the levels of various hormones, including insulin, glucose, triglyceride, and protein concentrations.

They found that insulin, glucose, and triglyceride levels were increased, while cortisol--a hormone released by the adrenal gland in response to stress--was decreased. Hormones, such as insulin and cortisol, help regulate metabolism and energy.

One of the reasons the study was undertaken, Abraham said, is that a horse treated with topical dexamethasone may test positive for doping, which could be a serious issue for a race horse.

"In race horses, doping is a serious issue, and as it is known, zero tolerance is the rule," Abraham said, adding that trainers need to be aware of the systemic effects of topical steroids before using them on race horses.

This doesn't mean the products shouldn't be used if needed, he said, but a trainer might consider the timing of the next race before applying them. Luckily the effects of the topical steroids are reversible, as blood levels return to normal.

The study, "Serum thyroid hormone, insulin, glucose, triglycerides and protein concentrations in normal horses: Association with topical dexamethasone usage," was published in June online ahead of print in The Veterinary Journal.

The abstract is available on PubMed.

About the Author

Marie Rosenthal, MS

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