Major bleeding risks of different low‐molecular‐weight heparin agents: a cohort study in 12 934 patients treated for acute venous thrombosis

Essentials Low‐molecular‐weight‐heparins (LMWH) kinetics differ which may result in different bleeding risks. A cohort of 12 934 venous thrombosis patients on LMWH was followed until major bleeding. The absolute major bleeding risk was low among patients registered at the anticoagulation clinic. Once‐daily dosing was associated with a lower bleeding risk as compared with twice‐daily. Summary Background Low‐molecular‐weight heparins (LMWHs) are considered members of a class of drugs with similar anticoagulant properties. However, pharmacodynamics and pharmacokinetics between LMWHs differ, which may result in different bleeding risks. As these agents are used by many patients, small differences may lead to a large effect on numbers of major bleeding events. Objectives To determine major bleeding risks for different LMWH agents and dosing schedules. Methods A cohort of acute venous thrombosis patients from four anticoagulation clinics who used an LMWH and a vitamin K antagonist were followed until they ceased LMWH treatment or until major bleeding. Exposures were classified according to different types of LMWHs and for b.i.d. and o.d. use. Cumulative incidences for major bleeding per 1000 patients and risk ratios were calculated and adjusted for study center. Results The study comprised 12 934 patients with a mean age of 59 years; 6218 (48%) were men. The cumulative incidence of major bleeding was 2.5 per 1000 patients (95% confidence interval [CI], 1.7–3.5). Enoxaparin b.i.d. or o.d. was associated with a relative bleeding risk of 1.7 (95% CI, 0.2–17.5) compared with nadroparin o.d. In addition, a nadroparin b.i.d. dosing schedule was associated with a 2.0‐fold increased major bleeding risk (95% CI, 0.8‐5.1) as compared with a nadroparin o.d. dosing schedule. Conclusions Absolute major bleeding rates were low for all LMWH agents and dosing schedules in a large unselected cohort. Nevertheless, twice‐daily dosing with nadroparin appeared to be associated with an increased major bleeding risk as compared with once‐daily dosing, as also suggested in a meta‐analysis of controlled clinical trials.