Once versus twice daily LMWH for the initial treatment of venous thromboembolism.

BACKGROUND: In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen.

OBJECTIVES: The objective of this review was to compare the efficacy and safety of once daily administration to a twice daily administration of LMWH.

SEARCH STRATEGY: Trials were identified through the Specialised Register of the Cochrane Peripheral Vascular Diseases Group (last searched May 2001), the Cochrane Controlled Trials Register (CCTR/CENTRAL) (last searched Issue 1, 2002), by hand-searching other relevant journals, by checking cross-references and through personal communication with experts.

SELECTION CRITERIA: Randomised clinical trials in which a once daily treatment regimen with LMWH is compared to a twice daily regimen in the initial treatment of patients with venous thromboembolism.

DATA COLLECTION AND ANALYSIS: Two reviewers assessed trials on criteria for inclusion and extracted the data independently.

MAIN RESULTS: Five studies were included with a total of 1508 patients. The pooled data showed a statistically non-significant difference in recurrent venous thromboembolism between the two treatment regimens (OR 0.82; 0.49 - 1.39). A comparison of major haemorrhagic events (OR 0.77; 0.40 - 1.45) and mortality (OR 1.14; 0.62 - 2.08) also showed a statistically non-significant difference between the two treatment regimens.

REVIEWER'S CONCLUSIONS: Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH. However, the 95% confidence interval implies that there is a possibility that the risk of recurrent VTE might be higher when patients are treated once daily. Hence the decision to treat the patient with a once daily regimen will depend on the evaluated balance between increased convenience and the potential for a lower efficacy.