Blood-thinning drug warfarin can double the risk of stroke

A widely used anti-clotting pill can double the risk of stroke when patients with a faulty heart rhythm first start taking it, a study has found. Researchers believe warfarin may deactivate two naturally occurring anti-clotting proteins before its blood-thinning effects are felt. After 30 days, the drug halves the risk of stroke.

Although only a small number of patients are believed to be at risk, the study authors urged doctors to be vigilant. Warfarin, originally developed as a rat poison, is the most commonly prescribed oral anti-clotting agent in the UK.