Antiplatelet therapy as secondary prevention of stroke or transient ischaemic attack

Aspirin reduces the risk of subsequent stroke by approximately 13% and of all vascular events by 20%. Low-dose aspirin is recommended, as doses above 300 mg daily have more adverse effects.

The combination of dipyridamole and aspirin is marginally more effective than aspirin alone, but has more adverse effects. It should be considered in patients who have recurrent cerebral ischaemic events despite aspirin therapy. The most common adverse effect of dipyridamole+aspirin is headache, and starting treatment with smaller doses may avoid it. One regimen is to continue once-daily aspirin in the morning and take dipyridamole+aspirin at night for the first week, then stop the aspirin and take dipyridamole+aspirin twice daily.

Clopidogrel is modestly more effective than aspirin in preventing serious vascular outcomes (ie stroke, myocardial infarction, vascular death). However, the absolute risk reduction is small and the drug costs more. Therefore, clopidogrel is mainly used as an alternative for patients who can't tolerate aspirin or have had recurrent cerebral ischaemic events while taking aspirin.

For initial antiplatelet therapy, use:

Dipyridamole alone can be used in patients who don't tolerate aspirin and clopidogrel—its efficacy is about the same as aspirin, but evidence supporting its use is limited.

A study of clopidogrel plus aspirin as short-term therapy¹ showed benefit, when started straight after minor ischaemic stroke or TIA and continued for up to 90 days. More randomised controlled trial evidence is needed before changing clinical practice.

The combination of clopidogrel plus aspirin for long-term secondary prevention after stroke or TIA has no benefit, because a reduction in ischaemic events is offset by an increase in serious bleeding. It may be continued, with care, in patients already taking the combination for clear cardiac indications (eg post–coronary artery stenting).