Veterinarians Now Have a Drug to Reduce Fever in Horses
In November 2019 the FDA approved the first and only medication for fever control in horses: dipyrone. Prior to this drug coming available, veterinarians were limited to using non-steroidal anti-inflammatory drugs to address febrile horses. During the 65th Annual American Association of Equine Practitioners Convention, held Dec. 7-11, 2019, in Denver, Colorado, Emily Sundman, DVM, clinical development manager at Kindred Biosciences, described the efficacy studies she’s done on the drug.

Dipyrone is a drug used in human and veterinary medicine for pain relief, fever reduction, muscle spasm suppression, and as an anti-inflammatory. In horses, veterinarians need to control fevers as quickly as possible to minimize deleterious systemic effects and improve patient well-being, Sundman explained.

To test dipyrone’s ability to reduce horses’ body temperature, she and her team conducted two studies on adult horses with respiratory infections and rectal temperatures of at least 102 degrees Fahrenheit.

Study 1

Sundman said they performed the first study, done without a placebo group, simply to determine what to expect from the drug. Her team gave eight affected horses a single intravenous (IV) 30 mg/kg dose of dipyrone and took rectal temperatures before drug administration and one, two, three, and six hours later.

Sundman said body temperatures decreased by at least one degree in seven horses (87.5%), and fevers disappeared completely in six (75%). Dipyrone rapidly and significantly reduced the horses’ temperatures at all four timepoints.

Study 2

The second study was randomized and placebo-controlled. The researchers took the rectal temperatures of 31 febrile horses before administering dipyrone, then four and six hours after. The following day horses crossed into the other treatment group, and the procedures were repeated in any still-febrile horses. Treated horses’ temperatures lowered significantly more than controls’ four and six hours post-treatment with dipyrone.

“Intravenous dipyrone can effectively reduce fever in horses with respiratory infection quickly (as early as one hour), with maximum effect at three to four hours, maintained over a six-hour period,” Sundman concluded.

She said the only symptoms her team noted were temporary changes in fecal consistency and clinical signs consistent with respiratory infection.

“This study provides supportive information for practitioners to evaluate horses post-treatment with dipyrone in clinical practice,” she said.