Evaluation of effects of rofecoxib on platelet function in an in vitro model of thrombosis with circulating human blood

BACKGROUND: Cyclooxygenase (COX)-2-selective non-steroidal anti-inflammatory drugs have been used for anti-inflammatory therapy. However, it has also been described that they may increase risk of cardiovascular events. OBJECTIVES: To study the effects of COX2 inhibitor rofecoxib on platelet function using in vitro tests. Results were compared with those obtained in a parallel experiment with acetyl salicylic acid (ASA). METHODS: Studies of platelet aggregation, using different agonists, were performed by a turbidimetric method. Adhesive and cohesive function of platelets were analyzed by perfusion techniques, treated blood was exposed to thrombogenic surfaces and platelet interaction was morphometrically evaluated. RESULTS: Twenty-five micro M of rofecoxib induced a prolonged lag time and a reduction in the percentage of aggregation when arachidonic acid, ADP or collagen were used as agonists. In perfusion studies with parallel chamber rofecoxib 50 microM and ASA 500 microM reduced overall platelet interaction with the collagen surface (17.4 +/- 3.7, P < 0.05; vs. 32.1 +/- 2.6%P < 0.05 and 17.9 +/- 2.4, vs. 31.9 +/- 3.24, P < 0.05, respectively). In studies performed on annular chambers, 25 micro M of rofecoxib reduced platelet interaction; values of the thrombus and covered surface were 17.4 +/- 4.5%; P < 0.05 and 21.1 +/- 4.1%; P < 0.05, respectively, vs. 30.4 +/- 7.5% and 33.5 +/- 6.5 in the control. ASA did also impair thrombus formation but differences did not reach the levels of statistical significance. Moreover, rofecoxib but not ASA reduced significantly thrombus height and thrombus area (7.4 +/- 0.5 microM; P < 0.005 and 96.0 +/- 21.2 microM(2); P < 0.05 vs. control 11.2 +/- 0.9 microM and 220.0 +/- 47.7 microM(2), respectively). CONCLUSION: We conclude that under our experimental conditions, rofecoxib diminished platelet aggregation induced by different agonists and inhibited platelet-mediated thrombogenesis in an in vitro model of thrombosis.