Thrombin generation was initiated with 0.2 pM human tissue factor (TF), 8.3 µM PC:PS vesicles, and 40 µg/ml CTI (plasma concentrations) in FIX/AT-depleted plasma supplemented with 100% recombinant FIX (90 nM) in the presence of increasing LMWH: 0 (●), 0.5 (○), 1 (■), 2.5 (□), 5 (▲), 10 (Δ), 20 (◆) and 40 µM (◇). Controls included no TF/recombinant FIX (▼) and 0.2 pM TF only (∇) in the absence of LMWH. The time course of thrombin generation was measured as described in Material and Methods. Thrombin generation curves represent the mean thrombin concentration over the first 40 min of assay from replicate determinations (n=3), and are identified by representative points. The relative velocity index for thrombin generation was plotted versus LMWH concentration and fitted as described in Materials and Methods to determine the EC50 for inhibition. Representative curves are presented.