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Uses & FDA Indications

Aspirin has two distinct therapeutic dose ranges: analgesic/anti-inflammatory doses for pain and fever, and lower antiplatelet doses for cardiovascular protection. Its FDA-approved uses reflect both applications.

• Pain relief — headache, toothache, menstrual cramps, muscle pain, minor arthritis
• Fever reduction — antipyretic in adults (not children, due to Reye's syndrome risk)
• Anti-inflammatory — rheumatoid arthritis, osteoarthritis (at higher doses under medical supervision)
• Acute myocardial infarction (heart attack) — chewing aspirin during a suspected heart attack reduces platelet clumping and limits clot size
• Secondary prevention of cardiovascular events — prevention of recurrent heart attacks and strokes in patients with established cardiovascular disease
• Ischemic stroke prevention — reducing risk of recurrent TIA and ischemic stroke
• Atrial fibrillation — in some patients unable to take anticoagulants
• Preeclampsia prevention — low-dose aspirin in high-risk pregnancies (as directed by an OB)
• Colorectal cancer prevention — growing evidence supports use in certain high-risk populations (not yet a broad OTC indication)

How It Works

Aspirin works by irreversibly inhibiting cyclooxygenase (COX) enzymes — both COX-1 and COX-2. It does this by covalently acetylating a serine residue at the active site of these enzymes, permanently blocking them. This is mechanistically distinct from other NSAIDs, which inhibit COX reversibly.

COX enzymes are responsible for converting arachidonic acid into prostaglandins and thromboxane A2. Inhibiting COX reduces:

• Prostaglandins — mediators of pain, inflammation, and fever
• Thromboxane A2 (TXA2) — a potent platelet activator and vasoconstrictor produced by COX-1 in platelets

At lower antiplatelet doses, aspirin preferentially inhibits platelet COX-1 (which makes TXA2) without completely suppressing vascular COX-2 (which produces protective prostacyclin). This selectivity is part of why low-dose aspirin provides cardiovascular protection without the same degree of GI harm as higher analgesic doses.

Side Effects

Common

• Stomach upset, nausea, heartburn
• GI irritation — even enteric-coated aspirin carries some GI risk
• Easy bruising due to platelet inhibition
• Prolonged bleeding from minor cuts
• Tinnitus (ringing in the ears) — often an early sign of salicylate toxicity at higher doses

Serious

• GI bleeding and peptic ulcers — COX-1 inhibition reduces the protective mucus lining of the stomach; major bleeding risk especially with chronic use or NSAID combination
• Hemorrhagic stroke — antiplatelet effect can increase bleeding risk in the brain
• Reye's syndrome — rare but potentially fatal condition in children and teenagers with viral illnesses given aspirin; affects brain and liver
• Aspirin-exacerbated respiratory disease (AERD) — bronchoconstriction and nasal polyp swelling triggered by aspirin in susceptible patients (Samter's triad)
• Salicylate toxicity — overdose causes tinnitus, sweating, hyperventilation, metabolic acidosis, and can be fatal
• Hypersensitivity reactions — urticaria, angioedema, anaphylaxis (rare)

Drug Interactions

Drug / Class	Interaction	Clinical Significance
Warfarin / Anticoagulants	Additive bleeding risk; aspirin inhibits platelets while warfarin inhibits clotting factors — combination substantially increases hemorrhage risk	High — use only when benefit clearly outweighs risk; monitor closely
Other NSAIDs (ibuprofen, naproxen)	Ibuprofen and naproxen can competitively block aspirin's access to COX-1 in platelets, potentially negating its antiplatelet effect if taken first	High — take aspirin at least 30 min before ibuprofen, or use a different NSAID
SSRIs / SNRIs	Serotonin reuptake inhibition reduces platelet serotonin, impairing clotting; combined with aspirin's antiplatelet effect, GI bleeding risk rises significantly	Moderate — consider adding GI protection
Methotrexate	Aspirin reduces renal clearance of methotrexate, leading to elevated and toxic methotrexate levels	High — avoid combination or reduce methotrexate dose with close monitoring
ACE inhibitors / ARBs	Higher aspirin doses may blunt the antihypertensive and cardioprotective effects of these agents	Moderate — low-dose aspirin generally acceptable; monitor BP
Valproic acid	Aspirin displaces valproic acid from protein binding and inhibits its metabolism, raising valproate levels and toxicity risk	Moderate — monitor valproate levels

Warnings & Contraindications

• Aspirin-exacerbated respiratory disease (AERD): Approximately 10% of asthmatic adults have AERD (Samter's triad). These patients experience severe bronchospasm and nasal symptoms after even small amounts of aspirin or NSAIDs. Contraindicated in known AERD.
• Bleeding disorders: Contraindicated in patients with active bleeding, hemophilia, or other coagulation disorders without careful risk-benefit evaluation.
• Pregnancy (third trimester): NSAIDs including aspirin can cause premature closure of the ductus arteriosus and oligohydramnios. Avoid after 20 weeks gestation unless specifically directed by a provider.
• Peptic ulcer disease: Active peptic ulcers are a relative contraindication. If aspirin is necessary, add a proton pump inhibitor (PPI) for GI protection.
• Surgery: Aspirin must typically be held 7–10 days before elective surgery due to permanent platelet inhibition. Always inform surgeons and anesthesiologists of aspirin use.
• Gout: Low-dose aspirin can raise uric acid levels and precipitate or worsen gout attacks.

FAQ

Should I take a daily aspirin to prevent heart disease?

The recommendation has changed significantly in recent years. The U.S. Preventive Services Task Force (USPSTF) no longer recommends initiating low-dose daily aspirin for primary prevention (no prior heart attack or stroke) in most adults over 60, as the bleeding risk outweighs the cardiac benefit in this group. For secondary prevention (patients who have already had a heart attack or stroke), daily aspirin remains an established recommendation. Discuss your individual risk with your provider.

What is enteric-coated aspirin and is it safer for the stomach?

Enteric-coated (EC) aspirin has a special coating that delays dissolution until the tablet reaches the small intestine, theoretically bypassing the stomach. However, studies show EC aspirin does not significantly reduce the risk of GI bleeding compared to regular aspirin, because most aspirin-related GI harm is caused by systemic prostaglandin suppression (reducing the stomach's protective mucus), not direct contact with the gastric lining. EC aspirin is absorbed more slowly and may be slightly less effective in acute situations like a suspected heart attack.

Can I take ibuprofen and aspirin together?

This combination is generally discouraged for two reasons: it significantly increases GI bleeding risk, and ibuprofen can block aspirin's access to platelet COX-1 — potentially negating aspirin's heart-protective effects. If you need an NSAID for pain while on daily aspirin for cardiovascular protection, take the aspirin first and wait at least 30 minutes before ibuprofen, or use a different analgesic (like acetaminophen) instead.

What happens in aspirin overdose?

Aspirin overdose (salicylate toxicity) is a medical emergency. Early symptoms include tinnitus, nausea, vomiting, and rapid breathing. As toxicity progresses it can cause severe metabolic disturbances (mixed respiratory alkalosis and metabolic acidosis), confusion, seizures, coma, and death. Call Poison Control (1-800-222-1222) or seek emergency care immediately if overdose is suspected. Treatment may include alkalinization of the urine, activated charcoal, or dialysis in severe cases.