Original Research Prognostic Significance of Oxidative Stress Markers in Colitis Associated with Phenylbutazone Administration in Draft Horses Maged El-Ashker PhD a , Sabry El-Khodery PhD a , Nadia Metwally PhD b , Hussein Hussein PhD c , Mohamed El-Boshy PhD d a Department of Internal Medicine and Infectious Diseases, Mansoura University, Mansoura, Egypt b Department of Medicinal Chemistry, National Research Centre, Dokki, Giza, Egypt c Department of Pathology, Mansoura University, Mansoura, Egypt d Department of Clinical Pathology, Mansoura University, Mansoura, Egypt article info Article history: Received 28 February 2011 Received in revised form 25 April 2011 Accepted 01 August 2011 Available online 29 October 2011 Keywords: Phenylbutazone Draft Horses Colitis Oxidative Stress Clinical Pathology abstract The present study was carried out to assess the prognostic significance of oxidative stress markers in draft horses with colitis associated with phenylbutazone administration under field condition. For this purpose, a total of 40 native breed draft horses were studied. Based on case history, physical examination, and postmortem findings, diagnosis was made. According to the clinical outcome, horses were categorized into survivors and nonsurvivors. Clinically, there was significant association between nonsurvivors and anorexia (P < .01), stasis of intestinal motility (P < .01), melena (P < .01), and diarrhea (P < .001). Biochemically, malondialdehyde and nitric oxide showed a significant increase (P < .05) in nonsurvivors compared with survivors, whereas activities of superoxide dismutase showed a significant decrease (P < .05). Analysis of receiver operating char- acteristic curve indicated a high sensitivity and specificity of malondialdehyde, nitric oxide, and superoxide dismutase levels (P < .001) to predict the clinical outcome of colitis. Additionally, total protein and albumin showed a significant decrease in non- survivors compared with survivors; however, aspartate aminotransferase, sorbitol dehydrogenase, urea, and creatinine showed an increase (P < .05). The present results suggest that estimation of oxidative stress markers and antioxidant parameters may be useful predictors of the clinical outcomes of colitis associated with phenylbutazone administration in draft horses. Ó 2012 Elsevier Inc. All rights reserved. 1. Introduction Nonsteroidal anti-inflammatory drugs (NSAIDs) are the cornerstone of treatment for many painful conditions in horses, including arthritis, laminitis, and colic [1,2]. Most NSAIDs are inhibitors of one or more of the cyclooxygenase (COX) enzymes. In general, there are two major COX isoenzymes: COX-1 is expressed in most tissues, whereas COX-2 is induced in inflammation. Both COX-1 and COX-2 use arachidonic acid to generate the same product, pros- taglandin H 2 . Several enzymes further modify this product to generate prostanoids, such as prostacyclin, thromboxane A 2 , and prostaglandins D 2 ,E 2 , and F 2 . These prostanoids influence gastrointestinal (GI), cardiovascular, immune, renovascular, pulmonary, central nervous system, and reproductive function [3]. It is now recognized that COX-2 is expressed in normal endothelial cells in response to shear stress, and that inhibition of COX-2 is associated with suppression of prostacyclin synthesis [4]. Presently, most COX inhibitors, including phenylbutazone, are nonselec- tive, meaning that they inhibit both COX-1 and COX-2 at therapeutic concentrations achieved in patients [5]. Although phenylbutazone is one of the most popular and Corresponding author at: Sabry El-Khodery, PhD, Internal Medicine and Infectious Diseases, Mansoura University, Mansoura 35516, Egypt. E-mail address: khodery@mans.edu.eg (S. El-Khodery). Journal of Equine Veterinary Science journal homepage: www.j-evs.com 0737-0806/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2011.08.008 Journal of Equine Veterinary Science 32 (2012) 146-152