The cyclooxygenase-2 (COX-2)-selective nonsteroidal antiinflammatory drugs (NSAIDs) are clinically useful for managing pain and inflammation in companion animals and humans. COX-2 drugs have been introduced to minimize COX-1 side effects on the gastrointestinal tract, kidneys, and platelets. The effects of 4 commonly prescribed NSAIDs (aspirin, carprofen, deracoxib, and meloxicam) on platelet function and 6-keto prostaglandin F1-alpha (6-keto PGF-alpha) and thromboxane (TXB2) levels were evaluated in 10 healthy dogs in this study. NSAIDs and placebo were administered in a random crossover design for 7 continuous days, followed by a 21-day washout. NSAIDs were administered at therapeutic dosages. Samples were collected before initial dosing on days 0 and 7. Platelet function was evaluated with a platelet-function analyzer, and aggregation was assessed with a dual-channel aggregometer. Other variables measured included 1-stage prothrombin time, activated partial thromboplastin time, fibrinogen concentration, and plasma 6-keto PGF-alpha and TXB2 concentrations. All dogs completed the study without negative drug effects. Hematocrit, platelet count, and white blood cell count did not differ before or after the study. Significant differences in platelet function were not identified after aspirin, carprofen, or meloxicam therapy. Platelet aggregation by the aggregation agonist adenosine diphosphate was mildly increased by deracoxib. Fibrinogen concentration was significantly decreased after meloxicam treatment. Other measures were unchanged after NSAID treatment. These results suggest that commonly used NSAIDs did not affect the systemic prosta-glandins measured in the study. Platelet aggregation was only mildly affected by deracoxib, and antiinflammatory aspirin dosages did not affect platelet aggregation.

Commentary: NSAIDs of the COX-2 variety have emerged as an important tool used to alleviate the significant pain and discomfort of many inflammatory conditions, particularly osteo-arthritis, in veterinary patients. An enhanced understanding of the pathophysiology of COX-2 NSAID metabolism and adverse effects will allow clinicians to choose medication appropriately for specific patients with comorbid conditions and special medication risks.

Effects of aspirin, carprofen, deracoxib, and meloxicam on platelet function and systemic prostaglandin concentrations in healthy dogs. Blois SL, Allen DG, Wood D, Conlon D. AM J VET RES 71:349-358, 2010.