Fluctuations in anti-factor Xa levels with therapeutic enoxaparin anticoagulation in pregnancy

Abstract

The objective of the study was to evaluate anti-factor Xa levels with therapeutic enoxaparin anticoagulation in pregnancy. A total of 15 pregnant subjects on therapeutic doses of enoxaparin (1 mg/kg +/-20% subcutaneously (s.c.) twice daily (b.i.d.)) were enrolled prospectively in this cross-sectional pilot project. Three blood levels for anti-factor Xa activity were examined: before the enoxaparin dose (trough), 3- to 4-h later (peak) and 8-h later. Anti-factor Xa activity level between 0.5 and 1.2 U/ml was considered therapeutic. Mean anti-factor Xa activity levels were: trough 0.45+/-0.18, peak 0.9+/-0.25 and 8-h after dose 0.72+/-0.23 U/ml. All peak levels were therapeutic; 20% (3/15) of the 8 h and 73% (11/15) of the trough levels were sub-therapeutic. Trough and 8-h post-dose anti-factor Xa activity levels were sub-therapeutic in a substantial number of patients receiving a b.i.d. regimen of therapeutic enoxaparin.