Key result
Prolonged phenylbutazone administration in horses caused hypoalbuminemia, neutropenia (<3.0 x 10^3 cells/microL), and changes in right dorsal colon arterial blood flow and VFA production.
Why the study?
Does phenylbutazone affect clinical and serum variables, colonic inflammation, and arterial blood flow in the right dorsal colon in healthy adult horses?
Observational (n=12)
Does phenylbutazone affect clinical and serum variables, colonic inflammation, and arterial blood flow in the right dorsal colon in healthy adult horses?
Prolonged phenylbutazone administration in horses causes significant pathophysiologic changes including hypoalbuminemia, neutropenia, and altered colonic blood flow and volatile fatty acid production.
May prompt albumin and neutrophil monitoring during prolonged equine phenylbutazone use; leaves open translation to clinical populations.
OBJECTIVE: To determine pathophysiologic effects of phenylbutazone on the equine right dorsal colon (RDC). ANIMALS: 12 healthy adult horses. PROCEDURES: A controlled crossover observational study was conducted. Clinical and serum variables, colonic inflammation (histologic grading), and measurement of myeloperoxidase (MPO) activity, malondialdehyde (MDA) and prostaglandin E(2) (PGE(2)) concentrations, ingesta volatile fatty acid (VFA) content, and arterial blood flow in the RDC were evaluated for a 21-day period in horses administered phenylbutazone (8.8 mg/kg, PO, q 24 h) or a control substance. RESULTS: Data from 8 horses were analyzed. Plasma albumin concentrations decreased significantly from days 10 to 21 during phenylbutazone treatment, compared with results during the same days for the control treatment. Phenylbutazone treatment caused neutropenia (< 3.0 x 10(3) cells/microL). No other clinical or hematologic abnormalities were detected for phenylbutazone or control treatments. Two horses developed colitis while receiving phenylbutazone. No significant differences were detected in the RDC between phenylbutazone and control treatments for MPO activity, MDA and PGE(2) concentrations, and histologic evidence of inflammation. Arterial blood flow in the RDC was significantly increased during phenylbutazone treatment, compared with values for the control treatment. Differences were identified in VFA production during phenylbutazone treatment, compared with the control treatment, with a decrease in acetic acid concentrations over time. CONCLUSIONS AND CLINICAL RELEVANCE: Prolonged phenylbutazone administration caused hypoalbuminemia, neutropenia, changes in RDC arterial blood flow, and changes in VFA production. Veterinarians should monitor serum albumin concentrations and neutrophil counts and be cautious when making dosing recommendations for phenylbutazone treatment of horses.
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McConnico et al. (2008) conducted an observational in Healthy (n=12). Phenylbutazone vs. Control substance was evaluated on Clinical and serum variables, colonic inflammation, MPO activity, MDA and PGE2 concentrations, VFA content, and arterial blood flow in the right dorsal colon. Prolonged phenylbutazone administration in horses caused hypoalbuminemia, neutropenia (<3.0 x 10^3 cells/microL), and changes in right dorsal colon arterial blood flow and VFA production.
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