Summary

Background. Low molecular weight heparin is as effective and safeas unfractionated heparin for treatment of acute venous thromboembolism.It is uncertain whether low molecular weight heparin should beadministered once-daily or twice-daily in this setting. Method. A metaanalysisof randomized studies which directly compared once- andtwice-daily administration of low molecular weight heparin for thetreatment of acute venous thromboembolism was performed. A literaturesearch was performed using Advanced Pub Med and the Cochranelibrary database, and abstracts from recent meetings were reviewed.Two investigators extracted data independently. Results. Five studies,involving 1522 patients, were eligible. There were no statisticallysignificant differences in the frequencies of symptomatic (odds ratio,0.85 in favor of once-daily therapy at three months, p = 0.6), andasymptomatic, recurrent venous thromboembolism; total and majorbleeds (odds ratio, 1.16 in favor of twice-daily therapy at 10 days,p = 0.8); and death, at 10 days, as well as at three months of follow-up.Conclusion. Once- daily low molecular weight heparin appears to be aseffective and safe as twice-daily administration for the acute treatmentof venous thromboembolism. However, there is inadequate data fromstudies that directly compared once-daily and twice-daily administrationto be able to exclude the possibility of a higher frequency of fatalbleeding with once-daily therapy.