Low-Molecular-Weight Heparins, Acenocoumarol and Bone Density

Accessible online at: www.karger.com/journals/hae Dear Sir, Recently, we published the results of a Polish multicentre trial which showed the efficacy of low-molecular-weight heparin (LMWH) when compared to acenocoumarol for secondary prophylaxis of VTE episodes [1]. However, a growing number of patients without reversible risk factors for VTE are assigned to periods of secondary prophylaxis extending beyond 6 months, because of a perceived high risk of late recurrence. Whether LMWH can be considered in this clinical context as an alternative to oral anticoagulants requires an update of our understanding of the adverse effects of this group of anticoagulants when administered over longer periods of time. We would like to share our initial experience regarding the risk of osteoporosis during secondary prophylaxis with LMWH in patients after VTE. Osteoporosis is a well-recognized complication of prolonged treatment with unfractionated heparin [2–4]. Generally, the intensity of bone structure disturbance is believed to depend on the total administered dose of unfractionated heparin. However, only a few published reports have directly addressed this problem since 1965. Only isolated publications report on the influence of UFH, LMWH and oral anticoagulants on bone structure [5, 6]. Our experience consists of a prospective observation of 54 patients (26 females, 28 males, age 22–75 years, average 56.7 years) assigned to secondary prophylaxis after episodes of VTE. Nadroparine (15,000 IU/day s.c.) was used in 15 patients, enoxaparine (1 mg/kg/ day s.c.) in 15 patients and acenocoumarol (administered to reach a target range of INR 2.0–3.0) in 24 patients. Each patient was evaluated for bone structure abnormalities twice: firstly after 10–14 days of initial treatment for VTE and then after either 3 months of secondary prophylaxis in those patients who received nadroparine or acenocoumarol or after 6–12 months in those receiving enoxaparine. Bone structure was assessed by densitometry (according to the DEXA method with LUNAR DPX-L, Lunar, Madison, Wisc., USA). Two different bones (femur and lumbar spine 2–4) were studied. The initial bone mineral density (BMD) as measured by densitometry was assigned a value of 100% and compared to the final BMD result, expressed as the percentage difference from the initial value. In addition, the Z score was assessed, defined for individual patients as the number of standard deviations from an ideal BMD value for age and sex subgroups.