Aspirin

How it works

It irreversibly acetylates platelet cyclo-oxygenase-1, blocking thromboxane A2 production and thereby inhibiting platelet aggregation for the lifetime of the platelet.

Prescribing in practice

• Haemorrhagic stroke must be excluded by imaging before starting, as aspirin increases bleeding risk; the main hazards are gastrointestinal and intracranial haemorrhage.
• Use with caution in active peptic ulceration, bleeding disorders and uncontrolled hypertension, and consider gastroprotection in those at risk.
• It is started promptly after confirmed ischaemic stroke and may be followed by longer-term antiplatelet therapy.

Monitoring

No routine laboratory monitoring is required, but watch for signs of gastrointestinal or other bleeding.

Counselling the patient

• Take with or after food to reduce stomach irritation.
• Report black stools, vomiting blood or unusual bruising.
• Tell clinicians you take aspirin before any surgery or dental work.

Evidence & guidelines

Early aspirin after acute ischaemic stroke is supported by the CAST and IST trials and recommended by NICE.