Medically Reviewed on 2/24/2022

Generic Name: aspirin

Brand Names: Bayer Buffered Aspirin, Durlaza, ASA, Bayer Children's Aspirin, Bayer Women's Low Dose, Bayer Low Adult Strength, Bayer Advanced Aspirin, Bayer Extra Strength, Bayer Extra Strength Plus, Bufferin, Bufferin Extra Strength, Ecotrin, Ecotrin Maximum Strength, Extended Release Bayer 8-Hour Caplets, Extra Strength Bayer Plus Caplets, Genuine Bayer Aspirin, Halfprin DSC, Maximum Bayer Aspirin, St. Joseph Adult Chewable Aspirin, St. Joseph Regular Strength, acetylsalicylic acid, Vazalore

Drug Classes: Antiplatelet Agents, Cardiovascular; Antiplatelet Agents, Hematologic; NSAIDs; Salicylates

What is aspirin, and what is it used for?

Aspirin (acetylsalicylic acid) is one of the oldest and most commonly used non-steroidal anti-inflammatory drugs (NSAIDs) for treating mild-to-moderate pain, fever, and inflammation from various causes. Because aspirin inhibits platelet aggregation and blood clotting, it is also used as prophylaxis to reduce the risk of heart disease and stroke that occur from blood clots blocking the blood vessels.

Aspirin works by inhibiting the activity of cyclooxygenases (COX-1 and COX-2), two enzymes that are essential for the biosynthesis of prostaglandin. Prostaglandin is a substance that has multiple functions in the body and plays a prominent role in inflammation and the resultant symptoms of pain and fever. Blocking the production of prostaglandin also inhibits the release of thromboxane A2, a substance that platelets produce to make the blood clot.

Aspirin’s effects are dose-dependent; aspirin inhibits clotting (antithrombotic) at low doses (75 to 81 mg/day), relieves pain (analgesic) and reduces fever (antipyretic) at intermediate doses (650 mg to 4 g/day), and it is anti-inflammatory at high doses (4 to 8 g/day). Use at high doses, however, poses the risk of salicylate toxicity that can cause hearing loss, tinnitus, and digestive issues.

Aspirin is available over-the-counter and on prescription in different forms and strengths under many different brand names. Aspirin is used in the treatment of the following conditions:




What are the side effects of aspirin?

Side effects of aspirin include:

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.


Medically speaking, the term "myalgia" refers to what type of pain? See Answer

What are the dosages of aspirin?

  • 81 mg
  • 325 mg
  • 500 mg

Tablet, delayed-release

  • 162mg
  • 325mg
  • 500mg

Tablet, chewable

  • 75 mg
  • 81 mg

Tablet, enteric-coated

  • 81 mg
  • 162 mg
  • 325 mg
  • 650 mg

Gum, chewing, oral

  • 227 mg

The extended-release capsule (Durlaza [Rx]) (adult only)

  • 162.5 mg


Pain and Fever

  • Adults: 325-650 mg orally/rectally once every 4-6 hours as needed
  • Controlled/extended/delayed-release products (enteric-coated): 650-1300 mg orally once every 8 hours; not to exceed 3.9 g/day

Acute Coronary Syndrome

For use as adjunctive antithrombotic effects for ACS (ST-segment elevation myocardial infarction [STEMI], unstable angina [UA]/non-ST-segment elevation myocardial infarction [NSTEMI])

Acute symptoms

  • 160-325 mg orally; chew non-enteric-coated tablet upon presentation (within minutes of symptoms)
  • If unable to take orally, may give 300-600 mg rectal suppository

Maintenance (secondary prevention)

  • 75-81 mg orally once/day indefinitely (preferred dose); may be taken as 81-325 mg/day
  • Regimen may depend on co-administered drugs or comorbid conditions
  • Co-administered with ticagrelor: 81 mg orally once/day

Percutaneous transluminal coronary angioplasty

  • Adjunctive aspirin therapy to support reperfusion with primary PCI (with or without fibrinolytic therapy)
  • Preoperative dose: 162-325 mg orally before the procedure
  • Maintenance: 81 mg orally once/day indefinitely (preferred dose) may give 81-325 mg/day
  • The regimen may depend on co-administered drugs or comorbid conditions
  • Co-administered with ticagrelor: 81 mg orally once/day

Primary and Secondary Prevention

Durazo: Indicated to reduce the risk of death and heart attack (myocardial infarction/MI) in patients with chronic CAD (e.g., history of MI, unstable angina, or chronic stable angina); also indicated to reduce the risk of death and recurrent stroke in patients who have had an ischemic stroke or transient ischemic attack (TIA)

The extended-release capsule (Durlaza [Rx]): 162.5 mg orally once/day

Use immediate-release aspirin, not extended-release capsule in situations where a rapid onset of action is required (such as acute treatment of myocardial infarction or before percutaneous coronary intervention)

Ischemic Stroke and Transient Ischemic Attack

  • 50-325 mg/day orally within 48 hours of stroke or TIA, then 75-100 mg/day orally


  • Up to 3 g/day orally in divided doses

Rheumatoid Arthritis

  • 3 g/day orally in divided doses; increased as needed for anti-inflammatory efficacy (target plasma salicylate, 150-300 mcg/mL)


  • 3.6-5.4 g/day orally in divided doses; monitor serum concentrations

Colorectal Cancer (Off-label)


  • 600 mg/day orally
  • Decreases risk of developing hereditary colorectal cancer (i.e., Lynch syndrome) by 60% if taken daily for at least 2 years

Dosing Modifications

Renal impairment

  • CrCl greater than 10 mL/min: Dose adjustment not necessary
  • CrCl less than 10 mL/min: Not recommended

Hepatic impairment

Severe liver disease: Not recommended


Pain and fever

Children under 12 years:

  • 10-15 mg/kg orally once every 4 hours, up to 60-80 mg/kg/day

Children 12 years and older:

  • 325-650 mg orally/rectally once every 4-6 hours as needed

Controlled/extended/delayed-release products (enteric-coated): 650-1300 mg orally once every 8 hours; not to exceed 3.9 g/day

Juvenile Rheumatoid Arthritis

  • Children less than 25 kg: 60-100 mg/kg/day orally divided every 6-8 hours (maintain serum salicylate at 150-300 mcg/mL)
  • Children 25 kg or more: 2.4-3.6 g/day

Kawasaki Disease

  • Febrile phase: 80-100 mg/kg/day orally divided every 6 hours for up to 14 days (48-72 hours after fever abates)
  • Maintenance: 3-6 mg/kg/day orally in single dose

Toxic dose: 200 mg/kg

What drugs interact with aspirin?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

Severe interactions of aspirin include:

Serious interactions of aspirin include:

Aspirin has moderate interactions with at least 257 different drugs.

Aspirin has mild interactions with at least 120 different drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

Aspirin is a pregnancy category D drug.

Avoid chronic or intermittent high doses of aspirin during pregnancy. Use aspirin only in life-threatening emergencies in the third trimester when no safer drug is available. There is positive evidence of human fetal risk. It is especially important that the patient does not use aspirin during the last 3 months of pregnancy unless specifically directed to do so by the doctor, because it may cause problems in the unborn child or complications during delivery.

  • Aspirin may affect maternal and newborn hemostasis mechanisms, leading to an increased risk of hemorrhage
  • High doses may also increase perinatal mortality by intrauterine growth restriction and teratogenic effects
  • Near term, aspirin may prolong gestation and labor
  • Premature closure of the ductus arteriosus may occur if used near term, with use of full-dose aspirin

FDA warns against the use of NSAIDs in pregnancy at 20 weeks or later because they can result in low amniotic fluid.

Aspirin enters breast milk. Decision to discontinue nursing or to discontinue aspirin should be made taking into account the importance of the drug to the mother.

Seek advice of health professional before using OTC aspirin during pregnancy


What else should I know about aspirin?

  • Aspirin should be discontinued if you develop tinnitus.
  • Individuals who consume three or more alcoholic drinks should be aware of bleeding risks associated with heavy alcohol use while taking aspirin.
  • Aspirin has gastrointestinal (GI) side effects, and physicians and patients should remain alert for symptoms of GI ulceration and bleeding, even in the absence of previous GI symptoms.

Subscribe to MedicineNet's General Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.


Aspirin (acetylsalicylic acid) is a non-steroidal anti-inflammatory drug (NSAID) used to treat mild-to-moderate pain, fever, and inflammation from various causes. Aspirin inhibits platelet aggregation and blood clotting, and is also used as prophylaxis to reduce the risk of heart disease and stroke that occur from blood clots. Do not take aspirin if you have bleeding gastrointestinal ulcers, ulcerative colitis, or hemorrhoids. Consult your doctor before taking aspirin if pregnant, as there is fetal risk when taken in the last trimester of pregnancy.

Treatment & Diagnosis

Medications & Supplements

Prevention & Wellness

FDA Logo

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 2/24/2022