Aspirin (acetylsalicylic acid)
Two very different use cases in one pill: low-dose for cardiovascular protection, and higher doses for pain and fever. The interaction profile is significant either way.
What it's used for
- Low-dose (81-100mg daily): secondary prevention after heart attack or stroke; sometimes primary prevention in selected high-risk patients.
- Standard dose (325-650mg): pain, fever, inflammation.
- Acute chest pain: chewed 325mg at the onset of suspected heart attack (per emergency guidance).
How it works
Irreversibly inhibits COX-1, reducing thromboxane and making platelets less sticky for their entire lifespan (~7-10 days). This is why stopping aspirin before surgery takes about a week.
Key interactions
- Warfarin, DOACs (apixaban, rivaroxaban): major — significantly increased bleeding risk.
- Ibuprofen: moderate — can blunt the cardioprotective effect of low-dose aspirin.
- SSRIs: moderate — additive bleeding risk.
- Clopidogrel: sometimes prescribed together intentionally (dual antiplatelet therapy) but requires careful monitoring.
- Alcohol: moderate — increases GI bleeding risk.
Common side effects
GI upset, heartburn, increased bruising. Ear ringing (tinnitus) at higher doses. Serious: GI bleeding, hemorrhagic stroke. Reye's syndrome risk in children with viral illness — aspirin is generally avoided under age 16 for fever.
Who should be cautious
- History of GI ulcers or bleeding.
- Planned surgery (usually held 5-7 days before).
- Bleeding disorders or on other blood thinners.
- Pregnancy (third trimester: avoid).
What to ask your pharmacist
- Do I still need daily aspirin given current guidelines?
- Should I take an enteric-coated version?
- What should I do before a dental or surgical procedure?