Once versus twice daily injections of low molecular weight heparin for the initial treatment of blood clots in the veins

Blood clots in the veins (venous thromboembolism (VTE)) can develop spontaneously or after surgery or bed rest. Venous thromboembolism can be life threatening if clots travel to the lungs. Blood-thinning drugs such as heparin are used to dissolve clots. Low molecular weight heparin (LMWH) can be given by injection, enabling people to leave hospital. The usual treatment is two injections a day, but once a day would be more convenient. This review included five studies with a combined total of 1508 participants. The combined data showed no statistically significant difference in recurrent VTE between the once daily and twice daily treatment regimens. A comparison of major bleeding events, improvement of the blood clot size and death also showed no statistically significant difference between the two treatment regimens. None of the five included studies reported information on post-thrombotic syndrome (ongoing swelling of the affected leg, pain, and skin changes). One daily injection with LMWH is therefore as effective and safe as twice daily injections.

Authors' conclusions: 

Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH.

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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. This is the second update of a review first published in 2003.

Objectives: 

To compare the efficacy and safety of once daily versus twice daily administration of LMWH.

Search strategy: 

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2013) and CENTRAL (2013, Issue 4).

Selection criteria: 

Randomised clinical trials in which LMWH given once daily is compared with LMWH given twice daily for the initial treatment of VTE.

Data collection and analysis: 

Two review authors assessed trials for inclusion and extracted data independently.

Main results: 

Five studies were included with a total of 1508 participants. The pooled data showed no statistically significant difference in recurrent VTE between the two treatment regimens (OR 0.82, 0.49 to 1.39; P = 0.47). A comparison of major haemorrhagic events (OR 0.77, 0.40 to 1.45; P = 0.41), improvement of thrombus size (OR 1.41, 0.66 to 3.01; P = 0.38) and mortality (OR 1.14, 0.62 to 2.08; P = 0.68) also showed no statistically significant differences between the two treatment regimens. None of the five included studies reported data on post-thrombotic syndrome.

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