Anti-Xa activity in obese patients after double standard dose of nadroparin for prophylaxis.

We measured anti-Xa activity before and at 2, 4, 9 and 12 h after subcutaneous injection of 0.3 ml nadroparin (2850 IU anti-Xa) in normal-weight volunteers (median bodyweight 71 kg, n=5) and compared them to the anti-Xa activity after subcutaneous injection of 0.6 ml nadroparin (5700 IU anti-Xa) in obese patients (median bodyweight 134 kg, n=8). The resulting median anti-Xa activity after 4 h was 1.4 times greater in the group of obese patients. This finding suggests that a linear, weight-adjusted increase in the prophylactic dose of nadroparin does not result in a linear increase of anti-Xa activity in obese patients.