Practice Safety Alerts

Safer treatment doses for low molecular weight heparins: summary of a safety report from the National Patient Safety Agency

BMJ 2010; 341 doi: (Published 02 November 2010) Cite this as: BMJ 2010;341:c5884
  1. Tara Lamont, special adviser1,
  2. David Cousins, head of medication safety1,
  3. Catherine Rosario, medication safety officer1
  1. 1National Reporting and Learning Service, National Patient Safety Agency, London W1T 5HD, UK
  1. Correspondence to: T Lamont tara.lamont{at}
  • Accepted 20 September 2010

Why read this summary?

Low molecular weight heparins such as enoxaparin are used to prevent and treat venous thromboembolism and to treat acute coronary syndromes. These medicines are given parenterally by intravenous or subcutaneous injection. They offer advantages over regular unfractionated heparin: they are seen as effective,1 with a low risk of heparin induced thrombocytopenia; patients are likely to spend less time in hospital because of the long duration of action and, where appropriate, subcutaneous administration. In the UK, low molecular weight heparins are considered the treatment of choice and are increasingly being used including outside hospital. Indicative figures for prescribing in England in 2008/092 suggest that over a third (1.1 million) of all enoxaparin doses of 60 ml or greater were prescribed in the community.

However, different clinical indications require different doses and frequency. For instance doses for treatment depend on the patient’s weight, unlike the standard doses given for prophylactic use. Underdosing can increase the risk of a further thromboembolic event, while overdosing can increase the risk of bleeding. Accurate dosing and careful monitoring is needed, particularly for those with renal impairment, because low molecular weight heparins are excreted through the kidneys.

Concerns about inconsistent use of prophlyaxis for venous thromboembolism has led to high-profile guidelines by the UK’s National Institute for Health and Clinical Excellence.3 But clinicians may be less aware of the potential for harm from errors in treatment doses. A recent audit of 16 hospitals in Wales showed that weight was not recorded in almost half of patients receiving low …

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