Efficacy and safety of low molecular weight heparin (ardeparin sodium) compared to warfarin for the prevention of venous thromboembolism after total knee replacement surgery: A double-blind, dose-ranging study

We performed a double-blind, randomized clinical trial to compare the efficacy and safety of three different subcutaneous (SC) low molecular weight heparin doses (ardeparin sodium 25, 35, or 50 anti-X(a) U/kg. twice daily [BID]) to adjusted-dose warfarin (international normalized ratio [INR] = 2.0 to 3.0), as venous thromboembolism prophylaxis after total knee replacement surgery, The primary endpoint was total venous thromboembolism prevalence, defined as deep vein thrombosis discovered at postoperative venography of the operated leg, or symptom atic, objectively-documented pulmonary embolism. Of 860 patients randomized, 680 (79%) had an evaluable venogram or pulmonary embolism. The total venous thromboembolism prevalence was significantly greater among patients prophylaxed with warfarin compared to ardeparin 50 BID (38% vs 27%, p = 0.019); the prevalence among ardeparin 25 BID (37%) and 35 BID (28%) patients was similar to warfarin and ardeparin 50 BID patients, respectively. Overt bleeding occurred in 22 (7.9%) ardeparin 50 BID patients compared to 12 (4.4%) warfarin patients (p = 0.08), and in seven ardeparin 25 and 35 BID patients each (5.2% and 5.0%, respectively). Compared to the warfarin group, blood loss was significantly greater in the ardeparin 50 and 25 BID groups, and not different in the ardeparin 35 BID group. Conclusions: Postoperative, unmonitored, fixed-dose ardeparin 50 anti-X(a) U/kg SC BID is significantly more effective than adjusted-dose warfarin for this indication. Although overt bleeding among warfarin and ardeparin 50 BID patients did not differ significantly, ardeparin 50 BID patients had significantly greater blood loss. Ardeparin 35 anti-X(a) U/kg SC BID may provide efficacy similar to ardeparin 50 anti-X(a) U/kg SC BID but with reduced bleeding.