In patients with a first episode of pulmonary embolism who took six months of anticoagulants, another 18 months of treatment with warfarin reduced the risk of blood clots and major bleeding, though the benefit was not maintained after discontinuing anticoagulation therapy, a study has shown. Findings from the study are published in JAMA.

Patients with a first episode of unprovoked venous thromboembolism are at higher risk of recurrent episodes when anticoagulant therapy is stopped after 3–6 months of treatment compared to those with a venous thromboembolism provoked by a transient risk factor (eg, surgery). For these high-risk patients, continuing anticoagulation past 3–6 months is linked to a reduction in the risk of recurrence. It is unclear, however, if the benefit is maintained thereafter.

Researchers from the Universite de Bretagne Occidentale, evaluated 371 adults who experienced a first episode of symptomatic unprovoked pulmonary embolism and was treated initially for six continuous months with a vitamin K antagonist. Patients were randomized to warfarin or placebo for 18 months with a median follow-up for 24 months.

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During the 18-month period, the composite of recurrent venous thromboembolism or major bleeding at 18 months (primary endpoint) occurred in 3% of patients in the warfarin group and 13.5% in the placebo group; this resulted in a relative risk reduction of 78%. The anticoagulation benefit was not seen after discontinuing therapy. During the total 42-month period, the composite outcome was seen in 21% of patients in the warfarin group and 24% in the placebo group.

Study findings suggest that more research is needed in long-term secondary prevention measures for these patients, whether they involve vitamin K antagonists, new anticoagulants, aspirin, or further customization according to patient risk furthers.

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