acetylsalicylic acid at a glance
Medicine class
NSAID analgesic and antiplatelet agent.
Main roles
Short-term relief of pain and fever, or prevention of further thrombotic cardiovascular and cerebrovascular events, depending on formulation.
Age restriction
Do not give to anyone under 16 unless specifically directed by a clinician.
Form matters
Effervescent tablets are dissolved in water; gastro-resistant tablets are normally swallowed whole and are unsuitable for rapid pain relief.
What is acetylsalicylic acid used for?
Licensed uses depend on the selected formulation.
Effervescent acetylsalicylic acid relieves headache, migraine, dental, menstrual, neuralgic, throat, muscular and rheumatic pain, and feverish colds or influenza symptoms.
Gastro-resistant acetylsalicylic acid is used for secondary prevention of thrombotic cardiovascular or cerebrovascular disease, including after myocardial infarction, unstable angina, ischaemic stroke, transient ischaemic attack or bypass surgery.
Clinician-recommended aspirin may be used during pregnancy to reduce pre-eclampsia risk in people with relevant risk factors.
How does acetylsalicylic acid work?
Acetylsalicylic acid inhibits cyclo-oxygenase enzymes and reduces prostaglandin production, producing pain-relieving, fever-reducing and anti-inflammatory effects. It also irreversibly reduces platelet activation and thromboxane formation, making platelets less able to form clots for the rest of their lifespan.
How to take acetylsalicylic acid
Follow the pack instructions or prescriber’s directions because administration differs by formulation.
Dissolve effervescent tablets fully in a glass of water before drinking.
Swallow gastro-resistant tablets whole with water; do not cut, crush or chew them because this damages the coating.
Taking aspirin with or after food may reduce indigestion.
Do not take antacids at the same time as gastro-resistant aspirin because they may cause premature release.
Tell clinicians and dentists that you take aspirin before an operation or dental procedure because its effect on platelets persists for several days.
acetylsalicylic acid side effects
Common or expected effects
- Indigestion, stomach discomfort or abdominal pain
- Bruising or bleeding more easily, such as prolonged bleeding from cuts
- Nausea or vomiting
Get urgent medical advice
- Stomach or intestinal ulceration or bleeding, including vomiting blood or black tar-like stools
- Severe allergy, including facial or throat swelling, wheezing, bronchospasm or anaphylaxis
- Bleeding within the brain or another major haemorrhage
- Severe skin or mucosal reactions
- Kidney or liver impairment
- Tinnitus, dizziness, vomiting, confusion or rapid breathing suggesting salicylate toxicity
acetylsalicylic acid in pregnancy
Aspirin can be used in pregnancy when recommended and monitored by a midwife, GP or specialist, including to reduce pre-eclampsia risk. Aspirin used for pain is not advised unless prescribed, especially from 20 weeks because of risks including reduced amniotic fluid and constriction of the fetal ductus arteriosus. Product-specific restrictions apply in the third trimester; discuss pregnancy or plans to conceive with the prescriber rather than starting or stopping prescribed aspirin independently.
acetylsalicylic acid while breastfeeding
acetylsalicylic acid interactions
Check prescribed, non-prescription and complementary products with a pharmacist or prescriber before combining them with aspirin.
Anticoagulants, antiplatelets and thrombolytics
Combined effects can substantially increase bleeding risk.
Other NSAIDs, including ibuprofen and naproxen
The combination increases gastrointestinal ulceration and bleeding; regular ibuprofen may also interfere with aspirin’s antiplatelet effect.
Common questions about acetylsalicylic acid
Answers are fully visible for fast scanning and source review.
Is acetylsalicylic acid the same as aspirin?
Yes. Aspirin is the commonly used name for acetylsalicylic acid.
Can it prevent another heart attack or stroke?
Selected gastro-resistant products are licensed for secondary prevention after thrombotic cardiovascular or cerebrovascular disease. They should be started only after clinical assessment.
Can it be used for a headache?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.