Effects of heparin and low-molecular-weight heparins on bone mechanical properties in rats.

Long-term administration of heparin can be associated with development of osteoporosis. The present study was carried out to compare the effects of standard heparin and two low-molecular-weight heparins (nadroparin and enoxaparin) on bone mechanical properties in rats. The experiment was conducted on 3-month-old female Wistar rats. Standard heparin was administered in doses of 1000 or 2000 IU/kg sc daily, nadroparin and enoxaparin were administered in doses of 1000 or 2000 anti-Xa IU/kg sc daily, for 28 days. Bone mass, length, diameter, mineral content and mechanical properties of the whole femur (extrinsic stiffness, ultimate and breaking load, deformation caused by the applied load) and the femoral neck (load at fracture) were examined. Standard heparin (2000 IU/kg sc daily) weakened the femoral neck. Enoxaparin and the higher doses of standard heparin and nadroparin induced similar unfavourable changes in mechanical properties of the whole femur; the changes were noticeable the most after administration of enoxaparin.