Aspirin in Stroke Patients: Does Dose Matter?

Written by: Joel Nelson, Ohio Northern University, PharmD Candidate

The American Stroke Association (ASA) released their updated guidelines for acute ischemic stroke management this year. They emphasized how to properly use aspirin in the treatment algorithm, in particular when to decrease doses from 325 mg/d to 81mg/d. This is due to side effects that a larger dose causes. GI bleeds are the main concern as a patient takes higher doses of aspirin. There are also concerns for GI bleeding when aspirin is given with other NSAIDs, excessive alcohol use and steroids. Enteric coated (EC) doses can help decrease the amount of bleeds, but it does not solve the issue completely. EC aspirin also absorbs at a slower speed, which could have an effect in overweight patients and people who need aspirin immediately.
One of the places 325mg aspirin is still used regularly is by neurologists to manage strokes and TIAs (Transient Ischemic Attack).   Immediately after a stroke or TIA, the CHEST guidelines recommend a dose of 160-326mg/d within 48 hours. After this acute treatment (1-2 weeks) the dose can be reduced to 75-100mg/d. Studies have been done that have compared doses as low as 30mg/d to 300mg/d and have found that the low dose is no less effective in preventing vascular events involving a stroke or TIA and has fewer adverse effects. There is evidence that higher doses of aspirin actually inhibit the anti-platelet actions.  The problem with taking lower doses is it takes longer to get the full amount of anti-platelet effects, therefore it is recommended for prevention of strokes to start at a higher dose (at least 120mg/d) for the first 3-5 days then lower the dose (30-81mg/d) for the duration of the prevention.
Jauch E, Saver J, Yonas H, et al. Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke; A Journal Of Cerebral Circulation [serial online]. March 2013;44(3):870-947. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed July 24, 2013.
A comparison of two doses of aspirin (30 mg vs. 283 mg a day) in patients after a transient ischemic attack or minor ischemic stroke. The Dutch TIA Trial Study Group. The New England Journal Of Medicine [serial online]. October 31, 1991;325(18):1261-1266. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed July 24, 2013.
Monagle P, Chan A, Vesely S, et al. Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest [serial online]. February 2012;141(2 Suppl):e737S-801S. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed July 24, 2013.
Joel Nelson 7/24/13 APPE

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