FPIN’s Clinical Inquiries

Aspirin in Patients with Acute Ischemic Stroke


Am Fam Physician. 2009 Feb 1;79(3):226-227.

Clinical Question

Does aspirin decrease morbidity or mortality in patients with acute ischemic stroke?

Evidence-Based Answer

Aspirin in a daily dose of 160 to 300 mg initiated within 48 hours of symptom onset results in a net decrease in morbidity and mortality caused by acute ischemic stroke (Strength of Recommendation [SOR]: A, based on a systematic review), regardless of the availability of computed tomography (CT). (SOR: A, based on a meta-analysis).

Aspirin is as effective as anticoagulants in this regard and causes less harm (SOR: A, based on a systematic review), but it should not be used in patients receiving thrombolytic therapy. (SOR: B, based on one randomized controlled trial [RCT]).

Ibuprofen (Motrin) may decrease aspirin’s effectiveness in acute ischemic stroke. (SOR: C, based on expert opinion).

Evidence Summary

Stroke is the third leading cause of mortality worldwide, with an estimated 30-day mortality of 10 percent. Of those who survive, 50 percent will require help for activities of daily living six months later. Approximately 80 percent of strokes are ischemic in origin.1 Despite advances in the treatment of other atherothrombotic diseases, such as acute coronary syndrome, treatment options for acute ischemic stroke remain limited.

A Cochrane systematic review summarized nine RCTs (n = 41,399) evaluating the use of aspirin in treating acute ischemic stroke.2 Six of the RCTs were double-blinded and placebo-controlled. Approximately 98 percent of the data was derived from two trials, the International Stroke Trial (IST; unblinded factorial design, no placebo)3 and the Chinese Acute Stroke Trial (CAST).4 Patients in these trials were treated with 160 to 300 mg of aspirin daily for two to four weeks, starting within 48 hours of the onset of symptoms. At a maximum of six months follow-up, aspirin therapy resulted in decreased odds of death or dependency (odds ratio [OR] = 0.94; 95% confidence interval [CI], 0.91 to 0.98; number needed to treat [NNT] = 77; cost of $58 per improved outcome5), recurrent ischemic stroke (OR = 0.77; 95% CI, 0.69 to 0.87; NNT = 143), and pulmonary embolism (OR = 0.71; 95% CI, 0.53 to 0.96; NNT = 1,000).

This Cochrane review also demonstrated increased odds of complete recovery (OR = 1.06; 95% CI, 1.01 to 1.11; NNT = 100), despite an increased risk of symptomatic intracranial hemorrhage (OR = 1.23; 95% CI, 1.00 to 1.50; number needed to harm [NNH] = 500) and major extracranial hemorrhage (OR = 1.68; 95% CI, 1.34 to 2.09; NNH = 250). Overall, the numbers needed to treat are relatively large; however, they outweigh the small but measurable risk from aspirin therapy. Clinical benefit may not be apparent to the individual physician, but it is evident on a population level.2

The Cochrane review confirmed the findings of a previous meta-analysis of the IST and CAST. This meta-analysis included subgroup analyses, which found no difference in effect of treatment based on time from onset of symptoms (zero to 48 hours), age, sex, level of consciousness, history of atrial fibrillation, heparin administration, CT findings, or previous CT scanning. Patients with a hemorrhagic stroke who were inadvertently randomized did not appear to be harmed by aspirin (16 percent death or further stroke compared with 18 percent for the control group).6 A double-blind, randomized, placebo-controlled trial of 441 patients evaluated the effects of aspirin 325 mg daily for five days on progression of acute ischemic stroke compared with placebo. Aspirin did not affect stroke progression during the treatment period (relative risk = 0.95; 95% CI, 0.62 to 1.45), at discharge, or at three months as measured by the Scandinavian Stroke Supervision Scale. This study was not powered to detect the size of effect reported in the Cochrane review and meta-analysis described above.7

Another Cochrane systematic review summarizing 15 trials (n = 16,558) compared anticoagulants (unfractionated heparin or low-molecular-weight heparin) versus aspirin in acute ischemic stroke. No significant difference was found in rates of death or dependency, recurrent stroke, neurologic deterioration, or deep venous thrombosis/pulmonary embolism. However, anticoagulants were associated with higher rates of symptomatic intracranial hemorrhage (OR = 2.27; 95% CI, 1.49 to 3.46), major extracranial hemorrhage (OR = 1.94; 95% CI, 1.20 to 3.12), and all-cause mortality (OR = 1.10; 95% CI, 1.01 to 1.29).8

Lastly, a posthoc analysis was performed on data from a randomized factorial trial of 622 patients with acute ischemic stroke. Patients receiving both thrombolytics and aspirin had increased mortality at three to 10 days compared with those receiving thrombolytics alone (OR = 2.1; 95% CI, 1.2 to 3.6). These deaths were more likely to be cerebral in origin (death preceded by neurologic deterioration or recurrent stroke), rather than extracerebral (OR = 2.0; 95% CI, 1.3 to 3.7), with a trend toward cerebral hemorrhage (OR = 2.2; 95% CI, 1.0 to 5.0).9

Recommendations from Others

The American Heart Association and the American Stroke Association Stroke Council recommend an initial aspirin dose of 325 mg within 24 to 48 hours of the onset of symptoms; however, not within 24 hours of thrombolytic therapy.10 The American College of Chest Physicians recommends aspirin 160 to 325 mg daily started within 48 hours in patients not receiving thrombolytic therapy.11

The U.S. Food and Drug Administration has issued a warning about the potential for concomitant ibuprofen use to decrease the antiplatelet effect of low-dose aspirin. Although it is unknown whether clinical end points are adversely affected, this interaction may be minimized by administering ibuprofen at least eight hours before or 30 minutes after an 81-mg dose of immediate-release (not enteric-coated) aspirin. Other nonsteroidal anti-inflammatory drugs should be considered to have the same potential effects unless proven otherwise.12

Clinical Commentary

The data are clear—in the setting of acute ischemic stroke, aspirin reduces the risk of death and recurrent stroke. Because it is inexpensive and well tolerated, it should be used routinely in this setting (although delayed one or two days after a thrombolysis attempt). However, physicians should keep in mind that other common clinical interventions, including blood pressure control, statin use, and smoking cessation, are each about three times more effective than aspirin at preventing future stroke. All these interventions must be integrated into the care of the patient with stroke for optimal long-term outcomes.

Author disclosure: Nothing to disclose.

Address correspondence by e-mail to Michael K. Park, MD, at Michael.park@uchsc.edu. Reprints are not available from the authors.


show all references

1. Warburton E. Stroke management. Clin Evid. 2007. http://clinicalevidence.bmj.com/ceweb/conditions/cvd/0201/0201-get.pdf. Accessed August 11, 2008....

2. Sandercock P, Gubitz G, Foley P, Counsell C. Antiplatelet therapy for acute ischaemic stroke. Cochrane Database Syst Rev. 2003;(2):CD000029.

3. The International Stroke Trial (IST): a randomised trial of aspirin, subcutaneous heparin, both or neither among 19435 patients with acute ischaemic stroke. International Stroke Trial Collaborative Group. Lancet. 1997;349(9065):1569–1581.

4. CAST: randomised placebo-controlled trial of early aspirin use in 20,000 patients with acute ischaemic stroke. CAST (Chinese Acute Stroke Trial) Collaborative Group. Lancet. 1997;349(9066):1641–1649.

5. Hankey GJ, Warlow CP. Treatment and secondary prevention of stroke: evidence, costs, and effects on individuals and populations. Lancet. 1999;354(9188):1457–1463.

6. Chen ZM, Sandercock P, Pan HC, et al. Indications for early aspirin use in acute ischemic stroke: a combined analysis of 40,000 randomized patients from the Chinese Acute Stroke Trial and the International Stroke Trial. On behalf of the CAST and IST collaborative groups. Stroke. 2000;31(6):1240–1249.

7. Rödén-Jüllig A, Britton M, Malmkvist K, Leijd B. Aspirin in the prevention of progressing stroke: a randomized controlled study. J Int Med. 2003;254(6):584–590.

8. Berge E, Sandercock P. Anticoagulants versus antiplatelet agents for acute ischaemic stroke. Cochrane Database of Syst Rev. 2002;(4):CD003242.

9. Ciccone A, Motto C, Aritzu E, Piana A, Candelise L. Negative interaction of aspirin and streptokinase in acute ischemic stroke: further analysis of the Multicenter Acute Stroke Trial-Italy. Cerebrovasc Dis. 2000;10(1):61–64.

10. Adams HP Jr, del Zoppo G, Alberts MJ, et al. Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups [published correction appears in Stroke. 2007;38(6):e38 and e96]. Stroke. 2007;38(5):1655–1711.

11. Albers GW, Amarenco P, Easton JD, Sacco RL, Teal P. Antithrombotic and thrombolytic therapy for ischemic stroke: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest. 2004;126 (3 suppl):483S–512S.

12. U.S. Food and Drug Administration. Concomitant use of ibuprofen and aspirin: potential for attenuation of the anti-platelet effect of aspirin. September 8, 2006. http://www.fda.gov/cder/drug/infopage/ibuprofen/Science_Paper.pdf. Accessed August 11, 2008.

Copyright Family Physicians Inquiries Network. Used with permission.


Clinical Inquiries provides answers to questions submitted by practicing family physicians to the Family Physicians Inquiries Network (FPIN). Members of the network select questions based on their relevance to family medicine. Answers are drawn from an approved set of evidence-based resources and undergo peer review. The strength of recommendations and the level of evidence for individual studies are rated using criteria developed by the Evidence-Based Medicine Working Group (http://www.cebm.net/levels_of_evidence.asp).

The complete database of evidence-based questions and answers is copyrighted by FPIN. If interested in submitting questions or writing answers for this series, go to http://www.fpin.org or e-mail: questions@fpin.org.


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