Low doses of aspirin reduce by 40% the recurrence of venous thrombosis and pulmonary embolism, affecting 130,000 people every year in Italy, with a high mortality rate (30,000 per year) and an equally high incidence of disability through the post-phlebitis syndrome (ulcers, varicose veins). To demonstrate the effectiveness of aspirin is a study on the New England Journal of Medicine conducted by Cecilia Becattini and Giancarlo Agnelli, of the University of Perugia.
"About 20% of patients with 'unjustified' venous thrombosis, i.e. which arises in the absence of a risk factor - the authors explain - has a relapse within two years after the end of the standard anticoagulant treatment of 6-12 months with vitamin K antagonists (warfarin, acenocoumarol). Continuing this therapy for longer prevents relapses, but increases the risk of bleeding, including serious ones". In practice, until now clinicians faced a dilemma: continuing an anticoagulant therapy put the patient at risk of bleeding but stopping it increased the risk of recurrence of thrombosis. In the WARFASA study (from the name of warfarin, the most widely used anticoagulant drug, and aspirin), Agnelli and Becattini conducted a double-blind trial in 400 patients who had a suffered from an "unjustified" thrombosis, and who had completed 6 to 18 months of standard warfarin therapy. Half of them were then randomized with low doses of aspirin (100 mg per day), the other half with a placebo for an observation period of 2 years: 28 patients taking aspirin had a recurrence of thrombosis, compared with the 43 taking placebo.
"We can conclude - says the study - that aspirin, administered following a traditional treatment with warfarin in patients who have had an "unjustified" venous thrombosis , is effective in reducing relapse, and does not lead to increased risk of bleeding, including serious ones. This therapy is therefore a potential alternative to avoid extending the anticoagulant therapy with warfarin over time".
Why is this all-Italian study published on a major clinical newspaper important? Venous thrombosis is the third cardiovascular disease in terms of frequency, following stroke and infarction.The study by Agnelli and Becattini marks a historic achievement: being able to extend the preventive effects of anticoagulant therapy without increasing the risk of bleeding. The Vitamin K antagonists such as warfarin have a greater effect compared to aspirin, because they reduce the risk of thrombotic recurrence by 80% (compared with only 40% of aspirin), but they also have a much greater risk of bleeding.How do you choose between the two drugs? It depends on the risk of recurrence of thrombosis: if this is high you choose warfarin, while when the risk is relatively low you choose aspirin.
Aspirin is very cheap and very safe: we have known it for 100 years, and the patient does not need to have any laboratory check done.
Finally, an important feature of the WARFASA study is that is was designed and conducted in a manner completely independent from the pharmaceutical industry, which certainly did not show any particular interest in conducting a clinical trial involving very low cost medicines such as aspirin and warfarin.