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Am Fam Physician. 1999;60(9):2671-2672

Low-molecular-weight heparins (LMWHs) are easier to use than unfractionated heparin because they can be administered subcutaneously once or twice daily, without the need for laboratory monitoring or dosage adjustment in most cases. Safety and efficacy studies of deep venous thrombosis treatment seem to lean toward LMWHs as having fewer major bleeding complications, fewer thromboembolic recurrences and reduced mortality rates.

Gould and associates performed a meta-analysis of treatment trials comparing LMWHs to unfractionated heparin in deep venous thrombosis treatment. A careful selection of studies looked at three major outcomes, including major bleeding during the initial heparin treatment period, recurrent thromboembolic events over three to six months and mortality rates over three to six months. Major bleeding complications occurred in 1.9 percent of the participants treated with unfractionated heparin. LMWHs seemed to reduce the risk of this complication, but the absolute risk reduction was small. Thromboembolic events occurred in 5.4 percent of all patients treated with unfractionated heparin. Again, the statistics slightly favored LMWHs as causing fewer episodes of thromboembolic events, but the difference was not statistically significant. Of all patients treated with unfractionated heparin, 6.8 percent died. There was a statistically significant reduction in death rate (29 percent) among patients treated with LMWHs. The mortality reduction with LMWHs was strikingly great in patients with cancer, but this phenomenon did not fully account for the death benefit imparted from use of LMWHs. No specific type of LMWHs seemed to have an advantage over any other.

The authors conclude that LMWHs reduce mortality rates after acute deep venous thrombosis and appear to be at least as safe as unfractionated heparin with regard to major bleeding complications and preventing thromboembolic recurrences.

In a related article, Gould and associates conclude that LMWHs are highly cost-effective for the inpatient management of venous thrombosis.

In an accompanying editorial, Weinstein points out that the minimally greater expense of initially giving patients LMWHs instead of unfractionated heparin is appropriately balanced by the improvement in outcomes. Well-conducted cost-effectiveness analyses can help to appropriately allocate revenues in health care.

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Copyright © 1999 by the American Academy of Family Physicians.

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