Aspirin

Aspirin commonly causes stomach upset and raises the chance of stomach ulcers and upper gastrointestinal bleeding, especially in older people, alcohol users, people taking other NSAIDs, and people taking anticoagulant or antiplatelet medications.

Short-term aspirin use at therapeutic doses may precipitate reversible acute kidney injury in patients with glomerulonephritis or cirrhosis; aspirin is contraindicated in some patients with chronic kidney disease.

Giving aspirin to children or adolescents for fever or viral illness can be associated with Reye syndrome, an uncommon but serious condition involving acute brain dysfunction and fatty changes in the liver.

Aspirin increases bleeding risk and is known to cause hemolytic anemia in people with glucose-6-phosphate dehydrogenase deficiency; it should not be used by people with hemophilia or other bleeding tendencies.

Aspirin causes an increased risk of cerebral microbleeds and intracerebral hemorrhage, with an estimated absolute risk increase of 12 events per 10,000 persons at average doses of 270 mg per day.

High doses may result in tinnitus (ringing in the ears).

For some individuals, aspirin can cause hives, swelling, headache, and angioedema appearing one to six hours after ingestion; aspirin may also delay healing of skin wounds.

Aspirin may worsen asthma and cause NSAID-precipitated bronchospasm in susceptible individuals.