Effects of Meloxicam and Phenylbutazone on Equine Gastric Mucosal Permeability

Abstract

Newer NSAIDs that more selectively target the induced isoform of the cyclooxygenase enzyme (COX2) activity might reduce adverse effects while preserving therapeutic benefits of these drugs. To compare the effect of oral administration of multiple dose rates of meloxicam and phenylbutazone (PBZ) on gastric mucosal integrity in horses. Twenty-five light breed horses. In vivo toxicity study. Horses were randomly assigned to 5 treatment groups, receiving placebo, PBZ (4.4 mg/kg PO q12h day 1, 2.2 mg/kg PO q12h for 4 days, 2.2 mg/kg PO q24h for 9 days), or 3 dose rates of meloxicam (0.6 mg/kg q24h, 1.8 mg/kg q24h, 3.0 mg/kg q24h) for 14 days. Sucrose permeability testing was performed on Day 0 (before treatment) and on Day 13. All personnel involved with data collection or analysis were blinded to treatment. Administration of PBZ at the above dose rate significantly increased gastric permeability to sucrose, evidenced by increased peak serum sucrose concentrations (280-1,580 pg/μL, P = .001) after treatment. Similar changes were not evident after administration of meloxicam at any dose rate tested, or in control horses (P > .05). Treatment was not associated with significant differences in ulceration of the squamous or glandular mucosa. Peak sucrose concentrations were not correlated with serum total protein or albumin concentrations (R(2) = -0.07, P = .61, R(2) = -0.08, P = .58, respectively). These results suggest that PBZ was associated with greater compromise to gastric mucosal integrity than meloxicam.