Horses with fever tend to be listless and off feed; they just don't feel well. Respiratory infection is a known source of fever. Recently a drug—dipyrone—was approved by the FDA for use in horses with the specific target of reducing fever. The study results were presented at the 2019 AAEP Convention.
To be included in the studies, horses older than one year of age had to be afflicted with a fever ≥ 102 degrees Fahrenheit due to respiratory disease. Rectal temperatures were monitored prior to intravenous dosing with dipyrone and at 1, 2, 3 and six hours post treatment. A second study looked at 31 horses in which rectal temperatures were obtained pre-dose, then 4 and 6 hours after treatment. Twenty-seven of those horses were placed in a second phase, with similar results of decreased rectal temperatures at 4 and 6 hours following IV administration.
The studies conclude that dipyrone is efficacious in decreasing fever within 1-4 hours following IV administration. Dipyrone should not be used in conjunction with other NSAIDs (phenylbutazone, flunixin meglumine, ketoprofen or firocoxib). The maximum effect seen is at 3-4 hours, and fever reduction was maintained over the six-hour study period.