title: Aspirin for preventing the recurrence of venous thromboembolism.
abstract: BACKGROUND
  About 20% of patients with unprovoked venous thromboembolism have a recurrence within 2 years after the withdrawal of oral anticoagulant therapy. Extending anticoagulation prevents recurrences but is associated with increased bleeding. The benefit of aspirin for the prevention of recurrent venous thromboembolism is unknown.
  
  
  METHODS
  In this multicenter, investigator-initiated, double-blind study, patients with first-ever unprovoked venous thromboembolism who had completed 6 to 18 months of oral anticoagulant treatment were randomly assigned to aspirin, 100 mg daily, or placebo for 2 years, with the option of extending the study treatment. The primary efficacy outcome was recurrence of venous thromboembolism, and major bleeding was the primary safety outcome.
  
  
  RESULTS
  Venous thromboembolism recurred in 28 of the 205 patients who received aspirin and in 43 of the 197 patients who received placebo (6.6% vs. 11.2% per year; hazard ratio, 0.58; 95% confidence interval [CI], 0.36 to 0.93) (median study period, 24.6 months). During a median treatment period of 23.9 months, 23 patients taking aspirin and 39 taking placebo had a recurrence (5.9% vs. 11.0% per year; hazard ratio, 0.55; 95% CI, 0.33 to 0.92). One patient in each treatment group had a major bleeding episode. Adverse events were similar in the two groups.
  
  
  CONCLUSIONS
  Aspirin reduced the risk of recurrence when given to patients with unprovoked venous thromboembolism who had discontinued anticoagulant treatment, with no apparent increase in the risk of major bleeding. (Funded by the University of Perugia and others; WARFASA ClinicalTrials.gov number, NCT00222677.).
authors.affiliation: Division of Internal and Cardiovascular Medicine and Stroke Unit, Department of Internal Medicine, University of Perugia, Perugia, Italy. cecilia.becattini@unipg.it
authors.forename: Cecilia
authors.initials: C
authors.lastname: Becattini
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Agnelli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Schenone
authors.forename: Sabine
authors.initials: S
authors.lastname: Eichinger
authors.forename: Eugenio
authors.initials: E
authors.lastname: Bucherini
authors.forename: Mauro
authors.initials: M
authors.lastname: Silingardi
authors.forename: Marina
authors.initials: M
authors.lastname: Bianchi
authors.forename: Marco
authors.initials: M
authors.lastname: Moia
authors.forename: Walter
authors.initials: W
authors.lastname: Ageno
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Vandelli
authors.forename: Elvira
authors.initials: E
authors.lastname: Grandone
authors.forename: Paolo
authors.initials: P
authors.lastname: Prandoni
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use; D001241:Aspirin / Q000009:adverse effects / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D011655:Pulmonary Embolism / Q000517:prevention & control; D055502:Secondary Prevention; D054556:Venous Thromboembolism / Q000188:drug therapy / Q000517:prevention & control*; D020246:Venous Thrombosis / Q000517:prevention & control; D014812:Vitamin K / Q000037:antagonists & inhibitors
chemical_list: D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D014812:Vitamin K; D001241:Aspirin