Clinical Decisionmaking

Injections of heparin seem to be safe and work as well as IV heparin for treating acute deep venous thrombosis

Patients afflicted with acute deep venous thrombosis (blood clots in a deep vein, usually of the leg or abdomen) have typically been treated in the hospital with intravenous, unfractionated heparin, an anticoagulant. A new study shows that subcutaneous injections once or twice daily of low-molecular-weight heparins (LMWHs) seem to be as safe and effective as conventional intravenous heparin. This certainly simplifies management of this condition, explains Alan M. Garber, M.D., Ph.D., of Stanford University. Unlike IV heparin, subcutaneous injections of heparin do not require laboratory monitoring of blood clotting times or dose adjustment in most cases. Furthermore, it may be possible to administer IV heparins on an outpatient basis.

With support from the Agency for Health Care Policy and Research (National Research Service Award training grant T32 HS00028), the researchers performed a meta-analysis of 11 randomized controlled trials that compared LMWH with unfractionated heparin for treatment of acute deep venous thrombosis. Compared with unfractionated heparin, LMWHs reduced mortality rates by 29 percent over 3 to 6 months of patient followup. However, LMWHs did not reduce their risk for death from major bleeding complications or documented thromboembolic recurrences. For major bleeding complications, the odds ratio favored LMWHs (OR, 0.57; 1 is equal odds), but the absolute risk reduction was small and not statistically significant (0.61 percent). For preventing thromboembolic recurrences, LMWHs seemed as effective as unfractionated heparin (OR, 0.85).

Considering these findings and the potential that LMWHs hold for outpatient management of selected patients, these agents may prove highly cost effective for treating venous thrombosis, despite their current higher price ($236 more per patient for the initial course of treatment compared with IV heparin). Future studies should explore the feasibility and safety of outpatient LMWH treatment in community settings, especially given the trend toward outpatient management of venous thrombosis.

See "Low-molecular-weight heparins compared with unfractionated heparin for treatment of acute deep venous thrombosis," by Michael K. Gould, M.D., M.Sc., Anne D. Dembitzer, M.D., Ramona L. Doyle, M.D., and others, in the May 18, 1999, Annals of Internal Medicine 130(10), pp. 800-809.

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