Randomized Blinded Controlled Trial of Dipyrone as a Treatment for Pyrexia in Horses

OBJECTIVE To evaluate the effectiveness and safety of dipyrone to control pyrexia in horses with naturally occurring disease under field conditions. ANIMALS 138 horses with pyrexia and various infections evaluated at 14 veterinary sites in 12 states. PROCEDURES In the first (effectiveness) phase of this 2-phase study, horses were randomly assigned 3:1 to receive 1 dose of dipyrone (30 mg/kg [13.6 mg/lb], IV) or an equivalent amount of placebo. Effectiveness was defined as a decrease in rectal temperature ≥ 1.1°C (2°F), compared with the pretreatment value, or a rectal temperature of ≤ 38.3°C (101.0°F) 6 hours after treatment administration. Horses deemed to have an appropriate reduction in rectal temperature (regardless of treatment group) by 6 hours were immediately entered into the safety phase of the study, in which dipyrone was administered IV at 30 mg/kg between 0 and 8 times up to every 8 hours on an as-needed basis, as determined by the clinical investigators. Horses were monit