In a recent research project at Louisiana State University, the effects of prolonged use of phenylbutazone (bute) were examined.The five researchers determined that prolonged use of bute can cause adverse effects in horses as soon as three days after initial treatment.
Effects of prolonged use of bute in horses
Researchers caution that equine veterinarians should monitor serum albumin concentrations and neutrophil counts and be extremely cautious when making dosing recommendations for phenylbutazone treatment.
The effects include protein loss, lowered white blood cell counts, blood-flow changes in the right dorsal colon and changes in volatile fatty acid activity.
During the study, eight horses were either administered bute at 8.8 mg/kg for 21 days, or were part of the control group given corn syrup. The horses were closely monitored using physical examinations, blood samples, arterial blood flow analysis examinations and samples collected from the right dorsal colon as well as other analyses.
Horses receiving bute experienced:
- Abnormally low protein concentrations in the blood stream beginning as early as three days after the initial administration of bute.
- A low number of white blood cells starting three to six days after initial treatment.
- Concentrations of one type of volatile fatty acid lowered significantly in just two weeks.
Two horses developed colitis while on bute and fluctuations occurred in the horse's reactions to the drug. Researchers noted that these fluctuations could affect a horse’s ability to perform.
The researchers cautioned that equine veterinarians should monitor serum albumin concentrations and neutrophil counts and be extremely cautious when making dosing recommendations for phenylbutazone treatment.
Support for this project was provided by the Grayson Jockey Club Research Foundation Incorporated.