Secondary prevention of ischaemic strokes: Effect of dosage of aspirin

Introduction and objective. The value of acetylsalicilic acid (AAS) in the secondary prevention of ischemic stroke is well established. However, the optimum dose of AAS for stroke-threatrened patients remains unsettled. This paper reviews the pattern of adverse reactions to AAS and their relationship to the dosage of AAS evaluated. Method. All the clinical trials in which AAS was used as the sole antiaggregant in the secondary prevention of ischemic stroke were reviewed. The crude odds ratio for the different adverse reactions was calculated using three sub tests: AAS versus placebo; AAS<330 mg/d versus AAS>330 mg/d; and each dosage level versus a placebo. Results. There is an increased risk associated with the use of AAS as compared to a placebo with respect to gastrointestinal bleeding (OR 2.3, IC 95% (1.6-4.1)), peptic ulcer (10.1 2.5-85.2)), intracerebral hemorrhage (2.2 (1.3-4)) and other hemorrhagic phenomena (2.6 (2-3.3)). Conclusions. There seems to be a direct relationship between the dosage of AAS and the frequency with which adverse reactions occur, except in the case of intracerebral hemorrhage. In the latter case there was no relationship with the dose give (0.8 (0.5-1.4)).