Effect of clopidogrel on tissue-plasminogen activator-induced in vitro thrombolysis of feline whole blood thrombi

Objective —To determine if clopidogrel enhanced the thrombolytic rate of tissue-plasminogen activator (t-PA) on an in vitro feline whole blood thrombosis model. Animals —9 purpose-bred cats. Procedure —Blood obtained from cats before (baseline) and after treatment with clopidogrel (75 mg, PO, q 24 h for 3 days) was anticoagulated with sodium citrate (9:1 volume-to-volume ratio) to which 1 µCi of I 125 - fibrinogen was added. Thrombi were formed by the addition of calcium chloride and bovine thrombin. Thrombi were placed into autologous plasma to which 0.1 mg of t-PA was added. Plasma samples were collected at different time points to determine the amount of released I 125 -fibrin split products. Thrombolytic rates were calculated by determining the time to 25%, 50%, and 75% thrombolysis (t 25 , t 50 , and t 75 , respectively). Confidence intervals for t 25 , t 50 , and t 75 at baseline were compared with those after treatment. Results —There were no significant differences in thrombolytic rates between values obtained at baseline and after clopidogrel treatment (t 25 , 18.0 vs 18.5 minutes; t 50 , 63.3 vs 65.6 minutes; and t 75 , 163.0 vs 170.1 minutes, respectively). Conclusions and Clinical Relevance —Clopidogrel did not have an effect on the rate of thrombolysis of feline whole blood thrombi induced by t-PA in this in vitro model. ( Am J Vet Res 2004;65:715–719)