Comparison of bleeding complications of warfarin and warfarin plus acetylsalicylic acid: a study in 3166 outpatients

Abstract. Objective. The aim of the study was to compare the incidence of bleeding complications in patients receiving warfarin alone and those receiving warfarin in combination with acetylsalicylic acid. Subjects and methods. This retrospective study comprises all outpatients in our hospital receiving warfarin (n = 3166) in the period 1 January 1986 to 31 December 1990. Of these, 2026 patients received warfarin alone, aiming at an international normalized ratio level of 4.2‐2.5, whereas the combination of warfarin and acetylsalicylic acid (150 mg daily) was given to 1140 patients, aiming at an international normalized ratio level of 2.8‐2.2. Total observation time represents 4420 treatment years. Results. A total of 175 bleeding episodes was observed, 18 of which were fatal, and 96 were serious (requiring hospitalization). The incidence of minor bleedings was significantly higher in the combined therapy group than in the group receiving warfarin alone, 2.9% and 1.4% respectively (P < 0.003). However, there was no difference in the therapy groups regarding the incidence of serious and fatal bleedings. The overall incidence of gastrointestinal bleedings was equal in the two groups. Conclusions. The combination of warfarin and aspirin 150 mg daily aiming at a less intense level of anticoagulation than in warfarin therapy alone does not increase the risk of major or fatal haemorrhage. 1994 Blackwell Publishing Ltd