The Effects of Nonsteroidal Anti-Inflammatory Drugs on Canine Hemostasis and Systemic Prostaglandin Levels
ACVIM 2008
S.L. Blois; D.G. Allen; R.D. Wood; P.D. Conlon
Ontario Veterinary College, University of Guelph
Guelph, ON, Canada

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in veterinary medicine to provide analgesic and anti-inflammatory benefits to patients. The adverse effects associated with NSAID use are believed to be largely due to inhibition of the enzyme cyclooxygenase (COX)-1. As such, COX-2-selective NSAIDs were developed in attempt to limit the development of NSAID-associated adverse effects. Recent reports in the human medical literature have suggested an increased incidence of thromboembolic events associated with the use of COX-2 selective NSAIDs. There is speculation that COX-2 selective NSAIDs may lead to an imbalance in cardiovascular prostaglandin levels, with a relative increase in thromboxane versus prostacyclin. Thromboxane promotes platelet aggregation and vasoconstriction, while prostacyclin counteracts these effects.

This study examined the effects of NSAIDs on hemostasis and prostaglandin levels in healthy dogs. Ten dogs were given four NSAIDs and one placebo in a cross-over design at dosages consistent with current therapeutic recommendations. The NSAIDs administered included aspirin, carprofen, deracoxib, and meloxicam. Parameters measured before and after 7 days of NSAID administration included platelet optical aggregometry, platelet function analysis (using the platelet function analyser, PFA-100, machine), and plasma thromboxane and prostacyclin levels.

Administration of NSAIDs did not cause a significant effect on platelet function measured by the PFA-100. Maximal platelet aggregation declined mildly after deracoxib administration. Rate of platelet aggregation was not affected by NSAID administration. Plasma thromboxane levels decreased after aspirin administration compared to levels after deracoxib administration, while NSAID administration did not affect plasma prostacyclin levels. The ratio of thromboxane to prostacyclin was not altered by NSAID administration. One-stage prothrombin time (OSPT), activated partial thromboplastin time (aPTT), and fibrinogen concentration were not affected by NSAID administration.

This study showed that treatment with COX-2 selective NSAIDs in healthy dogs did not result in increased platelet function or an imbalance in plasma thromboxane and prostacyclin levels at the tested dosages.

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Shauna Blois

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