Cosmi B, Hirsh J
Hamilton Civic Hospitals Research Centre, Ontario, Canada.
Curr Opin Cardiol. 1994 Sep;9(5):612-8. doi: 10.1097/00001573-199409000-00017.
Low molecular weight heparins are derived from unfractionated heparin by chemical or enzymatic depolymerization; as a result, the mean molecular weight of unfractionated heparin is reduced by about one third and its biochemical and pharmacologic properties are improved. Demonstrated advantages of low molecular weight heparins over unfractionated heparin are the greater bioavailability at low doses, the longer half-life, and the more predictable dose response, which allows for fixed doses to be administered without laboratory monitoring; a potential advantage is the reduced hemorrhagic-to-thrombotic ratio observed in experimental animals. Clinical studies in the prevention of venous thromboembolism have shown that whereas the advantages offered by low molecular weight heparin over unfractionated heparin are modest in general surgery, they are substantial when compared with these and other agents in orthopedic surgery. In addition, low molecular weight heparins are at at least as safe and effective as unfractionated heparin in the treatment of established deep vein thrombosis, but have the advantage that they can be administered once or twice daily without laboratory monitoring and can be used to treat uncomplicated deep venous thrombosis on outpatient basis.
低分子量肝素是通过化学或酶解聚从未经分级的肝素衍生而来；因此，未经分级的肝素平均分子量降低约三分之一，其生化和药理特性得到改善。低分子量肝素相对于未经分级的肝素已证实的优势包括低剂量时更高的生物利用度、更长的半衰期以及更可预测的剂量反应，这使得可以在无需实验室监测的情况下给予固定剂量；一个潜在优势是在实验动物中观察到的出血与血栓形成比率降低。预防静脉血栓栓塞的临床研究表明，虽然低分子量肝素相对于未经分级的肝素在普通外科手术中的优势一般，但与骨科手术中的这些及其他药物相比则很显著。此外，低分子量肝素在治疗已形成的深静脉血栓方面至少与未经分级的肝素一样安全有效，但具有可以在无需实验室监测的情况下每日给药一次或两次，并且可用于门诊治疗非复杂性深静脉血栓的优势。
