Objective To determine effects of anti-inflammatory doses of COX-2 selective NSAIDs carprofen, meloxicam, and deracoxib on platelet function in dogs and urine 11-dehydro-thromboxane B2.
Study design Randomized, blocked, crossover design with a 14-day washout period.
Animals Healthy intact female Walker Hounds aged 1–6 years and weighing 20.5–24.2 kg.
Methods Dogs were given NSAIDs for 7 days at recommended doses: carprofen (2.2 mg kg−1, PO, every 12 hours), carprofen (4.4 mg kg−1, PO, every 24 hours), meloxicam (0.2 mg kg−1, PO, on the 1st day then 0.1 mg kg−1, PO, every 24 hours), and deracoxib (2 mg kg−1, PO, every 24 hours). Collagen/epinephrine and collagen/ADP PFA-100 cartridges were used to evaluate platelet function before and during and every other day after administration of each drug. Urine 11-dehydro-thromboxane B2 was also measured before and during administration of each drug.
Results All NSAIDs significantly prolonged PFA-100 closure times when measured with collagen/epinephrine cartridges, but not with collagen/ADP cartridges. The average duration from drug cessation until return of closure times (collagen/epinephrine cartridges) to baseline values was 11.6, 10.6, 11 and 10.6 days for carprofen (2.2 mg kg−1 every 12 hours), carprofen (4.4 mg kg−1 every 24 hours), meloxicam and deracoxib, respectively.
Conclusions and clinical relevance Oral administration of some COX-2 selective NSAIDs causes detectable alterations in platelet function in dogs. As in humans, PFA-100 collagen/ADP cartridges do not reliably detect COX-mediated platelet dysfunction in dogs. Individual assessment of platelet function is advised when administering these drugs prior to surgery, particularly in the presence of other risk factors for bleeding.