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Am J Vet Res. 2008 Nov;69(11):1496-505. doi: 10.2460/ajvr.69.11.1496.

Pathophysiologic effects of phenylbutazone on the right dorsal colon in horses.

Author information

1
Department of Veterinary Clinical Sciences, Equine Health Studies Program, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.

Abstract

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.

PMID:
18980433
DOI:
10.2460/ajvr.69.11.1496
[Indexed for MEDLINE]
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