ENOXAPARIN, A LOW-MOLECULAR-WEIGHT HEPARIN SUPPRESSES PROTHROMBIN ACTIVATION MORE EFFECTIVELY THAN UNFRACTIONATED HEPARIN IN PATIENTS TREATED FOR VENOUS THROMBOEMBOLISM

Although unfractionated heparin (UFH) is standard therapy for venous t hromboembolism, there is a clinical failure rate of up to 10%. Newer t reatment strategies include low-molecular-weight heparins (LMWH). As p art of an international study comparing the efficacy and safety of eno xaparin, a LMWH versus UFH in patients with venous thromboembolism, we studied the effects of enoxaparin and UFH on the plasma concentration s of two activation peptides, fragment 1+2 (F1+2), and thrombin-antith rombin III (TAT) complexes. We hypothesized that enoxaparin would be m ore effective in suppressing activation of coagulation. Intravenous he parin was given by bolus injection followed by infusion. There were 2 enoxaparin treatment groups (1 mg/kg s.c., bid and 1.5 mg/kg s.c. dail y). Plasma samples were obtained from 11 patients in the enoxaparin gr oup and 6 patients in the heparin group prior to and at 6 hour interva ls after initiating therapy. Clinical characteristics of the enoxapari n and UFH patient groups were similar. TAT concentrations were not sta tistically different between groups at any treatment interval. However , plasma F1+2 concentrations differed significantly (p < 0.05); concen trations in the enoxaparin group were consistently lower over time tha n in the UFH group. These results suggest that this LMWH is more effec tive in suppressing ongoing thrombosis in vivo than UFH in patients wi th venous thrombosis. (C) 1997 Elsevier Science Ltd.