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09/09/2009 - Articles

Warfarin risks and benefits revealed

By: Susan Aldridge, medical journalist, PhD


Warfarin is an anticoagulant drug that is used in treatment of atrial fibrillation (AF), a condition affecting as many as 2.3 million Americans.  In AF, the upper chambers of the heart beat out of sync, which can increase the risk of blood clotting and ischemic stroke. 

Warfarin helps by thinning the blood but it can be a tricky drug to take, because it also increases the risk of brain haemorrhage, so patients must be carefully monitored when taking it.  Indeed, warfarin is linked to the most emergency hospital admissions for adverse drug effects.  In one of the first, and largest, studies of its kind, Kaiser Permanente and  Massachusetts General Hospital researchers set out the risks and benefits of warfarin.


They followed nearly 14,000 patients with AF between 1996 and 2003, recording their age and medical histories, as well as cases of ischemic stroke and brain haemorrhage.  By using a ‘real world’ setting, the researchers believe they have a more accurate assessment of warfarin than older studies give.  Overall, warfarin did give some benefit to most AF patients through reducing their risk of ischemic stroke.  But the benefit was far greater for the ‘oldest old’ (over 85) and for those with multiple stroke risk, including those with a history of stroke.  Patients under 65 derived no clear benefit from warfarin.  These new findings will be very useful to physicians thinking of prescribing warfarin to patients with AF.  They will be able to balance the benefits and risks involved based upon clear information and will be able to pinpoint those patients who may be at risk of an adverse drug effect from warfarin and have them more closely monitored.  In short, it looks as if warfarin is a drug which has more to offer the older patient.



Singer DE, Chang Y et al The net clinical benefit of warfarin anticoagulation in atrial fibrillation Ann Int Med September 1 2009;151:297-305

Created on: 09/09/2009
Reviewed on: 09/09/2009

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