Aspirin – side effects, dosage and low-dose

  1. Aspirin- Side Effects, Dosage, Interactions – Drugs
  2. Aspirin Warnings
  3. Pregnancy and Aspirin
  4. Aspirin for Dogs and Cats
  5. Low-Dose Aspirin
  6. Anti-Inflammatory Actions Key
  7. Aspirin Isn’t Right for Everyone
  8. Zorprin, Bayer Buffered Aspirin (aspirin) dosing, indications, interactions, adverse effects, and more
  9. Acute Coronary Syndrome
  10. Acute symptoms
  11. Maintenance (secondary prevention)
  12. Percutaneous transluminal coronary angioplasty
  13. Primary ASCVD Prevention with Low-Dose Aspirin
  14. Ischemic Stroke & Transient Ischemic Attack
  15. Anti-Inflammatory
  16. Colorectal Cancer (Off-label)
  17. Renal impairment
  18. Minor
  19. Absolute
  20. Relative
  21. Cautions
  22. Lactation
  23. Pregnancy Categories
  24. Absorption
  25. Distribution
  26. Metabolism
  27. Elimination
  28. Aspirin: Dosage & Side Effects
  29. Dosage
  30. Baby aspirin or low-dose aspirin
  31. Aspirin for dogs
  32. Aspirin: Side Effects, Dosages, Treatment, Interactions, Warnings
  33. Dosages of Aspirin
  34. Pain and Fever
  35. Primary and Secondary Prevention
  36. Ischemic Stroke and Transient Ischemic Attack
  37. Rheumatoid Arthritis
  38. Juvenile Rheumatoid Arthritis
  39. Spondyloarthropathy
  40. Kawasaki Disease (Pediatric)
  41. Dosing Considerations, Pediatric
  42. Aspirin Uses, Dosage, Side Effects & Interactions –
  43. What is aspirin?
  44. Important information
  45. Before taking this medicine
  46. How should I take aspirin?
  47. What happens if I miss a dose?
  48. What happens if I overdose?
  49. What should I avoid while taking aspirin?
  50. What other drugs will affect aspirin?
  51. Further information
  52. Related questions
  53. Aspirin – side effects, dosage and low-dose
  54. How does aspirin work?
  55. Aspirin for pain and fever
  56. Aspirin for heart disease and stroke
  57. Side effects of aspirin
  58. Types of aspirin
  59. Dosage of aspirin
  60. Taking daily low-dose aspirin
  61. Who should not take aspirin?
  62. Is aspirin safe in pregnancy?
  63. Can I take aspirin while breastfeeding?
  64. References

Aspirin- Side Effects, Dosage, Interactions – Drugs

Aspirin - side effects, dosage and low-dose

Aspirin is medication used to treat fever, pain, and inflammation in the body.

It also prevents blood clots, stroke, chest pain, and heart attack in certain people.

This drug comes in an over-the-counter (OTC) and prescription form, in a variety of brand names, and is also found in many combination products.

Aspirin is in a group of drugs called salicylates, which work by stopping the production of prostaglandin, substances in the body that cause inflammation.

There is some evidence that aspirin may reduce the risk of developing cancer, especially colorectal cancer. Aspirin is also sometimes used to treat rheumatic fever (a condition that can develop after strep throat) and Kawasaki disease (an illness that can cause heart problems in kids).

The Food and Drug Administration (FDA) approved Bayer aspirin in 1965.

Aspirin Warnings

Before taking aspirin, tell your doctor if you have or have ever had:

  • Asthma
  • Frequent stuffed or runny nose
  • Nasal polyps (growths on the linings of the nose)
  • Frequent heartburn, upset stomach, or stomach pain
  • Ulcers
  • Anemia
  • Gout
  • Diabetes
  • Liver or kidney disease
  • Hemophilia (a bleeding disorder) or any other bleeding conditions

You should ask your doctor before giving aspirin to a child or teenager. The medicine can cause a serious and sometimes fatal condition known as Reye's syndrome.

Tell your doctor you are taking aspirin before having any type of surgery, including dental procedures. Also, tell your healthcare provider you are taking this medicine before having any type of lab work, as aspirin may interfere with the results.

You shouldn't take aspirin to treat pain for longer than 10 days or to treat a fever that lasts longer than three days, as this may signal a more serious condition.

Talk to your doctor if you have surgery to remove your tonsils to determine which types of pain medication are safe to take.

If you take aspirin regularly to prevent a heart attack or stroke, you shouldn't take ibuprofen (Advil, Motrin) or other non-steroidal anti-inflammatory drugs (NSAIDs, such as naproxen or diclofenac) to treat pain without first talking to your doctor.

Aspirin may cause stomach/intestinal bleeding and ulcers. Older adults may be more ly to suffer from this side effect.

Pregnancy and Aspirin

Taking aspiring during pregnancy may harm an unborn baby's heart, reduce birth weight, or cause other effects. You should talk to you doctor if you are pregnant or plan to become pregnant while taking aspirin.

The medicine can also pass into breast milk and may harm a breastfeeding baby. You shouldn't breastfeed while taking aspirin.

Aspirin for Dogs and Cats

Aspirin may be given to dogs to relieve pain. Some veterinarians recommend using buffered aspirin (e.g., Bufferin), given with food, to prevent digestive problems.

However, aspirin must be administered with extreme care when given to cats.

Small doses of aspirin can produce a loss of appetite, depression, and vomiting. Talk to your veterinarian before giving your dog or cat this drug.


Low-Dose Aspirin

Aspirin - side effects, dosage and low-dose

US Pharm. 2018;43(2):11-12.

Aspirin is one of the oldest, most widely used drugs in the world. Taken for pain relief for over 2,000 years, its active ingredient, salicin, is in the leaves and bark of the willow tree.

In 1897, the Bayer company in Germany developed a synthetic version called acetylsalicylic acid and named it aspirin. The regular adult dosage is 650 mg taken every 4 hours when needed to treat pain, inflammation, and fever caused by a variety of ailments.

Low-dose aspirin refers to dosages between 81 mg and 325 mg taken every day to prevent heart attacks, strokes, and colon cancer.

Most heart attacks and strokes happen when a blood clot forms and blocks blood flow in an artery. Under normal circumstances, the body develops a blood clot to stop the loss of blood after an injury.

When a blood vessel is damaged, sticky cells called platelets begin to clump together, while proteins in the blood form strands of fibrin. The fibrin creates a net- structure that holds the forming clot together.

Blood clots can form in damaged vessels of the heart or the brain, and these can block blood to the tissue and cause a heart attack or stroke. Aspirin stops clots from forming by preventing the platelets from clumping together.

If you have had a heart attack or stroke, your doctor may prescribe low-dose aspirin to prevent a second event. Low-dose aspirin has been shown to reduce the risk of a first heart attack but has not been definitively proven to reduce the risk of a stroke. Speak with your physician before starting low-dose aspirin for prevention.

Anti-Inflammatory Actions Key

Aspirin is also a nonsteroidal anti-inflammatory drug (NSAID), which means that it reduces inflammation, although it is not a steroid cortisone or prednisone. Similar to the formation of blood clots, inflammation is the body’s natural response to injury.

When an injury occurs, the immune system is activated, and compounds called prostaglandins form in the area surrounding the injury. Prostaglandins increase blood flow to the injury, leading to the redness, heat, and swelling associated with inflammation.

Aspirin prevents these prostaglandins from forming, reducing inflammation.

It is aspirin’s anti-inflammatory action that also makes it useful in the prevention of colon cancer and in preeclampsia, a serious condition of pregnancy believed to result from an inflammatory response. Recent research has also found regular aspirin use to be associated with lower rates of breast, prostate, lung, and ovarian cancer.

Aspirin Isn’t Right for Everyone

Even in low doses, aspirin can have significant side effects. The most common ones, occurring in up to 10% of people who take aspirin, are an increased tendency to bleed and stomach upset, including heartburn, nausea, vomiting, or bleeding in the stomach. Other less common side effects include kidney, liver, and nervous system problems.

Although low-dose aspirin is an OTC drug and safe for most people, the FDA recommends that certain individuals not take aspirin in any dose.

Those with an allergy to aspirin or salicylates; those with a bleeding disorder such as hemophilia or vitamin K deficiency; and people with uncontrolled high blood pressure, severe liver or kidney disease, or asthma should avoid using aspirin.

In addition, aspirin should not be used by someone who is also taking a prescription blood thinner such as warfarin, Pradaxa, or Xarelto, or another OTC NSAID such as naproxen (Aleve) or ibuprofen (Advil).

Before taking any OTC drug on a regular basis, even low-dose aspirin, be sure to talk with your healthcare provider first to find out if it’s right for you. Always ask your pharmacist to check your prescription and other OTC medications for aspirin interactions or incompatibilities. Even supplements such as fish oil and vitamin D can interact with aspirin.

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Zorprin, Bayer Buffered Aspirin (aspirin) dosing, indications, interactions, adverse effects, and more

Aspirin - side effects, dosage and low-dose

Immediate release: 325- 650 mg PO q4hr PRN or 975 mg PO q6hr PRN or 500-1,000 mg PO q4-6hr for no more than 10 days; not to exceed 4 g/day

Rectal: 300-600 mg PR q4hr for no more than 10 days or as directed by health care provider

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 PO; chew nonenteric-coated tablet upon presentation (within minutes of symptoms)
  • If unable to take PO, may give 300-600 mg suppository PR

Maintenance (secondary prevention)

  • 81-325 mg PO qDay indefinitely (preferred dose); may give 81-325 mg/day
  • Regimen may depend on coadministered drugs or comorbid conditions
  • Extended-release capsule (Durlaza [Rx]): 162.5 mg PO qDay

Percutaneous transluminal coronary angioplasty

  • Adjunctive aspirin therapy to support reperfusion with primary PCI (with or without fibrinolytic therapy)
  • Preprocedure: 162-325 mg PO before procedure
  • Postprocedure: 81 mg PO qDay indefinitely (preferred dose) may give 81-325 mg/day
  • Regimen may depend on coadministered drugs or comorbid conditions
  • Coadministered with ticagrelor: 81 mg PO qDay

Primary ASCVD Prevention with Low-Dose Aspirin

Adults aged 40-70 years: Consider use of low-dose aspirin (75-100 mg PO qDay) for select adults who are at higher risk for atherosclerotic cardiovascular disease (ASCVD), but not at increased bleeding risk (AHA/ACC 2019 Guidelines on Primary Prevention of Cardiovascular Disease)

Adults aged >70 years: Low-dose aspirin should not be administered on a routine basis for primary prevention of ASCVD

Any age with increased bleeding risk: Do not administer low-dose aspirin for primary prevention

Note: There may be select circumstances where clinicians might discuss prophylactic aspirin with adults aged 70 yr in the context of other known ASCVD risk factors (eg, strong family history of premature MI, inability to achieve lipid or BP or glucose targets, or significant elevation in coronary artery calcium score)

Ischemic Stroke & Transient Ischemic Attack

Initial: 160-325 mg PO within 48 hr of stroke/TIA onset, followed by 75-100 mg PO qDay

AHA/ASA recommends an initial dose of 325 mg within 24-48 hr after stroke; do not administer aspirin within 24 hr after administration of alteplase


Use of non-aspirin NSAIDs has largely supplanted the use of aspirin for osteoarthritis, rheumatoid arthritis, and other inflammatory arthritides

Immediate release: Usual maintenance dose: 2.1-7.3 g/day in divided doses (individualize dose); monitor serum salicylate concentrations

Colorectal Cancer (Off-label)


600 mg/day PO

Decreases risk of developing hereditary colorectal cancer (ie, Lynch syndrome) by 60% if taken daily for at least 2 years

Renal impairment

  • CrCl >10 mL/min: Dose adjustment not necessary
  • CrCl


All Interactions Sort By: SeverityName



CNS alteration

Dermatologic problems

GI pain, ulceration, bleeding


Hearing loss


Platelet aggregation inhibition

Premature hemolysis

Pulmonary edema (salicylate-induced, noncardiogenic)


Renal damage




Hypersensitivity to aspirin or NSAIDs; aspirin-associated hypersensitivity reactions include aspirin-induced urticaria (HLA-DRB1*1302-DQB1*0609 haplotype), aspirin-intolerant asthma (HLA-DPB1*0301)

Allergy to tartrazine dye


  • Bleeding GI ulcers, hemolytic anemia from pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G6PD) deficiency, hemophilia, hemorrhagic diathesis, hemorrhoids, lactating mother, nasal polyps associated with asthma, sarcoidosis, thrombocytopenia, ulcerative colitis


  • Appendicitis, asthma (bronchial), chronic diarrhea, bowel outlet obstruction (for enteric-coated formulations), dehydration, erosive gastritis, hypoparathyroidism


Anemia, GI malabsorption, history of peptic ulcers, gout, hepatic disease, hypochlorhydria, hypoprothrombinemia, renal impairment, thyrotoxicosis, vitamin K deficiency, renal calculi, ethanol use (may increase bleeding)

Discontinue therapy if tinnitus develops

Should be taken with food or 8-12 oz of water to avoid GI effects

Not indicated for children with viral illness; use of salicylates in pediatric patients with varicella or influenza illness is associated with increased incidence of Reye syndrome

Heart Failure (HF) risk

  • NSAIDS have the potential to trigger HF by prostaglandin inhibition that leads to sodium and water retention, increased systemic vascular resistance, and blunted response to diuretics
  • High-dose aspirin (greater than 325mg) should be avoided or withdrawn whenever possible
  • AHA/ACC Heart Failure Guidelines; Circulation. 2016; 134

Avoid chronic or intermittent high doses during pregnancy; 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

Seek advice of health professional before using OTC drugs during pregnancy


Drug enters breast milk; a decision should be made regarding whether to discontinue nursing or to discontinue drug, taking into account importance of drug to mother

Seek advice of health professional before using OTC drugs while breastfeeding

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.

Inhibits synthesis of prostaglandin by cyclooxygenase; inhibits platelet aggregation; has antipyretic and analgesic activity


Bioavailability: 80-100%

Onset: PO, 5-30 min; PR, 1-2 hr

Duration: PO, 4-6 hr; PR, >7 hr

Peak plasma time: PO, 0.25-3 hr

Peak plasma concentration: Analgesia/antipyresis, 30-100 mcg/mL; anti-inflammatory, 150-300 mcg/mL


Protein bound: ≤100 mcg/mL, 90-95%; 100-400 mcg/mL, 70-85%; higher concentrations, 25-60%

Vd: 170 mL/kg


Metabolized by liver via microsomal enzyme system

Metabolites: Salicylurate, salicyl phenolic glucuronide, salicyl acyl glucuronide, 2,5-dihydroxybenzoic acid (gentisic acid), 2,3-dihydroxybenzoic acid, 2,3,5-trihydroxybenzoic acid, gentisuric acid (active)

Enzymes inhibited: Cyclooxygenase (insignificant)


Half-life: Low dose, 2-3 hr; higher dose, 15-30 hr

Renal clearance: 80-100% in 24-72 hr

Excretion: Urine (80-100%), sweat, saliva, feces

Dialyzable: Yes

FormularyPatient Discounts

Adding plans allows you to compare formulary status to other drugs in the same class.

To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

Adding plans allows you to:

  • View the formulary and any restrictions for each plan.
  • Manage and view all your plans together – even plans in different states.
  • Compare formulary status to other drugs in the same class.
  • Access your plan list on any device – mobile or desktop.

Medscape prescription drug monographs are FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.


Aspirin: Dosage & Side Effects

Aspirin - side effects, dosage and low-dose

Aspirin is a pain reducer available in both prescription and non-prescription forms. It works by stopping the production of natural substances that cause pain, swelling, fever or blood clots. Aspirin is a part of salicylate drug group and is a non-steroidal, anti-inflammatory drug (NSAID). It is sometimes found in combination with other antacids, pain relievers or cold medication.

Non-prescription aspirin is commonly used to lessen mild-to-moderate pain caused by headaches, toothaches, muscle aches, colds, menstrual cramps or arthritis. It is also often used to reduce fever. Additionally, aspirin can be a preventive medicine for a variety of ailments, including heart attacks, some strokes, and blood clots in patients with artificial heart valves.

Non-prescription aspirin can be used to help prevent heart attacks in people who have angina (chest pain that occurs from the heart not getting enough oxygen) or who have had a heart attack in the past. It may also reduce the risk of death for people who are experiencing or who have recently had a heart attack. [Countdown: 5 Interesting Facts About Aspirin]

In terms of strokes, non-prescription aspirin may help prevent ischemic strokes (which occur when a blood clot blocks the flow of blood to the brain) or mini-strokes (which occur when blood flow to the brain is blocked for a short period of time). It cannot help prevent hemorrhagic strokes, which are caused by bleeding in the brain.

Prescription aspirin may help relieve symptoms of rheumatoid arthritis, osteoarthritis, lupus and other rheumatologic conditions, in which the immune system attacks part of the body. It is also sometimes used to treat rheumatic fever and Kawasaki disease, which may cause heart problems in children.


Aspirin can be taken orally or rectally. Non-prescription aspirin is available as a tablet, delayed-release tablet, chewable tablet, powder, gum and suppository. Prescription aspirin is available as an extended-release tablet.

Non-prescription aspirin can be taken every 4 to 6 hours as needed to reduce pain or fever, and once a day at a lower dose to reduce the risk of heart attack or stroke. Prescription aspirin is usually taken two or more times per day.

The extended-release tablets should be taken with a full glass of water and never broken, crushed or chewed. It is a good idea to drink water after taking any form of aspirin, as it may cause stomach pain.

Delayed-release tablets take some time to go into effect, so they are not the best option for those suffering from pain or fever that must be relieved quickly.

A doctor should be consulted before a child or teenager takes aspirin. Taking aspirin can cause Reye’s syndrome in children or teenagers, especially if they have had a virus such as chicken pox or the flu. Reye’s syndrome is a serious condition in which fat builds up in the brain, liver, and other body organs.

Aspirin may cause side effects. The NIH lists the following as less serious, though a doctor should be consulted if they persist:

  • nausea
  • vomiting
  • stomach pain
  • heartburn

The following are serious side effects, and, if experienced, a doctor should be consulted immediately:

  • hives
  • rash
  • swelling of the eyes, face, lips, tongue, or throat
  • wheezing or difficulty breathing
  • hoarseness
  • fast heartbeat
  • fast breathing
  • cold, clammy skin
  • ringing in the ears
  • loss of hearing
  • bloody vomit
  • vomit that looks coffee grounds
  • bright red blood in stools
  • black or tarry stools

Patients with bleeding disorders such as hemophilia should not take aspirin. Those taking it for stroke or heart attack prevention should not also take ibuprofen, as it can make aspirin less effective.

Everyone should be careful about taking other over-the-counter medicines while taking aspirin as many of them contain aspirin, and the combination can lead to overdose.

[Related: What's the Difference Between Tylenol and Aspirin?]

Patients should not drink alcohol while taking aspirin.

Pregnant women should consult their doctors before taking aspirin. Taking aspirin while pregnant can potentially cause fetal damage. New mothers should not take aspirin while breastfeeding.

Baby aspirin or low-dose aspirin

Most patients taking aspirin to prevent heart attack or stroke take “baby” or low-dose aspirin (However, baby aspirin has never been intended for infants). The standard baby aspirin dose is 81 mg, and doses as low as 75 mg are available. Regular-strength aspirin is 325 mg. Patients should talk to their doctors about the correct dosage.

Aspirin for dogs

Pet owners should consult a veterinarian before giving a dog aspirin. Depending on the dog and the situation, buffered or enteric-coated aspirin (available over-the-counter) can be reasonably safe for dogs.

Unbuffered or coated aspirin, however, can cause serious gastrointestinal problems.

Aspirin is no longer the recommended long-term treatment for dogs with arthritis, though sometimes it can be helpful for short-term use.

Aspirin can interact with dogs’ other medicines. Dogs with bleeding or clotting disorders should not take it. It can also cause birth defects; so pregnant animals should not take it.

Individual dogs will metabolize aspirin at very different rates, which can lead to problems in determining the correct dose and lead to dangerous breakdown products from aspirin to accumulate in the animals’ body.

For example, two regular-strength aspirins can lead to severe organ damage in some — but not necessarily all — medium-sized dogs.

This metabolism inconsistency is one reason why it is important for pet owners to meet with vets before administering medicine.

Aspirin is not safe for cats to take. Any drugs containing acetaminophen can be lethal for both cats and dogs.

Further reading:


National Library of Medicine


Aspirin: Side Effects, Dosages, Treatment, Interactions, Warnings

Aspirin - side effects, dosage and low-dose

Aspirin is used to reduce fever and relieve mild to moderate pain from conditions such as muscle aches, toothaches, common cold, and headaches. It may also be used to reduce pain and swelling in conditions such as arthritis.

Aspirin is known as a salicylate and a nonsteroidal anti-inflammatory drug (NSAID). It works by blocking a certain natural substance in your body to reduce pain and swelling.

Consult your doctor before treating a child younger than 12 years.

Your doctor may direct you to take a low dose of aspirin to prevent blood clots. This effect reduces the risk of stroke and heart attack. If you have recently had surgery on clogged arteries (such as bypass surgery, carotid endarterectomy, coronary stent), your doctor may direct you to use aspirin in low doses as a “blood thinner” to prevent blood clots.

Aspirin is available under the following different brand names: Zorprin, Bayer Buffered Aspirin, Durlaza, Asatab, Adprin-B, Alka-Seltzer Extra Strength with Aspirin, Alka-Seltzer with Aspirin, Arthritis Pain Formula, Ascriptin, Ascriptin Maximum Strength, 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, Empirin, Extended Release Bayer 8-Hour Caplets, Extra Strength Bayer Plus Caplets, Genuine Bayer Aspirin, Halfprin, Maximum Bayer Aspirin, St. Joseph Adult Chewable Aspirin, St. Joseph Regular Strength, and acetylsalicylic acid.

Dosages of Aspirin


Tablet, delayed-release

Tablet, chewable

Tablet, enteric-coated

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

Gum, chewing, oral

Extended-release capsule (Durlaza [Rx]) (adult only)

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

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

Primary and Secondary Prevention

Durlaza: 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)

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 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

Rheumatoid Arthritis

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

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


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

Kawasaki Disease (Pediatric)

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

Dosing Considerations, Pediatric

Toxic dose: 200 mg/kg


Aspirin Uses, Dosage, Side Effects & Interactions –

Aspirin - side effects, dosage and low-dose

Generic Name: aspirin (oral) (AS pir in)
Brand Names:Arthritis Pain, Aspir 81, Aspir-Low, Bayer Childrens Aspirin, Durlaza, Ecotrin, Ecpirin, Fasprin, Halfprin, Miniprin

Medically reviewed by Sanjai Sinha, MD Last updated on Dec 1, 2018.

What is aspirin?

Aspirin is a salicylate (sa-LIS-il-ate). It works by reducing substances in the body that cause pain, fever, and inflammation.

Aspirin is used to treat pain, and reduce fever or inflammation. It is sometimes used to treat or prevent heart attacks, strokes, and chest pain (angina).

Aspirin should be used for cardiovascular conditions only under the supervision of a doctor.

Important information

You should not use aspirin if you have a bleeding disorder such as hemophilia, a recent history of stomach or intestinal bleeding, or if you are allergic to an NSAID (non-steroidal anti-inflammatory drug) such as Advil, Motrin, Aleve, Orudis, Indocin, Lodine, Voltaren, Toradol, Mobic, Relafen, Feldene, and others.

Do not give this medication to a child or teenager with a fever, flu symptoms, or chicken pox. Salicylates can cause Reye's syndrome, a serious and sometimes fatal condition in children.

Before taking this medicine

Do not give this medicine to a child or teenager with a fever, flu symptoms, or chicken pox. Aspirin can cause Reye's syndrome, a serious and sometimes fatal condition in children.

You should not use aspirin if you are allergic to it, or if you have:

  • a recent history of stomach or intestinal bleeding;
  • a bleeding disorder such as hemophilia; or
  • if you have ever had an asthma attack or severe allergic reaction after taking aspirin or an NSAID (non-steroidal anti-inflammatory drug) such as Advil, Motrin, Aleve, Orudis, Indocin, Lodine, Voltaren, Toradol, Mobic, Relafen, Feldene, and others.

To make sure this medicine is safe for you, tell your doctor if you have:

  • asthma or seasonal allergies;
  • stomach ulcers;
  • liver disease;
  • kidney disease;
  • a bleeding or blood clotting disorder;
  • gout; or
  • heart disease, high blood pressure, or congestive heart failure.

Taking aspirin during late pregnancy may cause bleeding in the mother or the baby during delivery. Tell your doctor if you are pregnant or plan to become pregnant.

Aspirin can pass into breast milk and may harm a nursing baby. You should not breast-feed while using this medicine.

How should I take aspirin?

Take aspirin exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Take with food if aspirin upsets your stomach.

Do not crush, chew, break, or open an enteric-coated or delayed-release pill. Swallow it whole.

The chewable tablet form must be chewed before swallowing.

If you use the orally disintegrating tablet or the dispersible tablet, follow all dosing instructions provided with your medicine.

If you need surgery, tell the surgeon ahead of time that you are using this medicine. You may need to stop using it for a short time.

Do not take this medicine if you smell a strong vinegar odor in the bottle. The medicine may no longer be effective.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Since aspirin is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include temporary hearing loss, seizure (convulsions), or coma.

What should I avoid while taking aspirin?

Avoid drinking alcohol while you are taking aspirin. Heavy drinking can increase your risk of stomach bleeding.

If you are taking this medicine to prevent heart attack or stroke, avoid also taking ibuprofen (Advil, Motrin). Ibuprofen may make this medicine less effective. If you must use both medications, take the ibuprofen at least 8 hours before or 30 minutes after you take the aspirin (non-enteric coated form).

Ask a doctor or pharmacist before using any cold, allergy, or pain medication. Many medicines available over the counter contain aspirin or an NSAID. Taking certain products together can cause you to get too much of this type of medication. Check the label to see if a medicine contains aspirin, ibuprofen, ketoprofen, naproxen, or an NSAID.

Get emergency medical help if you have signs of an allergic reaction to aspirin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using this medicine and call your doctor at once if you have:

  • ringing in your ears, confusion, hallucinations, rapid breathing, seizure (convulsions);
  • severe nausea, vomiting, or stomach pain;
  • bloody or tarry stools, coughing up blood or vomit that looks coffee grounds;
  • fever lasting longer than 3 days; or
  • swelling, or pain lasting longer than 10 days.

Common aspirin side effects may include:

  • upset stomach, heartburn;
  • drowsiness; or
  • mild headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect aspirin?

Ask your doctor before using aspirin if you take an antidepressant such as citalopram, escitalopram, fluoxetine (Prozac), fluvoxamine, paroxetine, sertraline (Zoloft), trazodone, or vilazodone. Taking any of these medicines with an NSAID may cause you to bruise or bleed easily.

Ask a doctor or pharmacist if it is safe for you to use aspirin if you are also using any of the following drugs:

  • a blood thinner (warfarin, Coumadin, Jantoven), or other medication used to prevent blood clots; or
  • other salicylates such as Nuprin Backache Caplet, Kaopectate, KneeRelief, Pamprin Cramp Formula, Pepto-Bismol, Tricosal, Trilisate, and others.

This list is not complete. Other drugs may interact with aspirin, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Further information

Remember, keep this and all other medicines the reach of children, never share your medicines with others, and use aspirin only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2020 Cerner Multum, Inc. Version: 15.02.

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Aspirin – side effects, dosage and low-dose

Aspirin - side effects, dosage and low-dose

Aspirin is one of the oldest medicines still in common use. It belongs to a class of medicines called salicylates and works by suppressing the production of certain substances in the body that cause pain, fever and inflammation.

Aspirin also affects platelets – cells in the blood that are involved in clotting. Taking aspirin reduces the ability of platelets to stick together and form clots, making it useful in the treatment and sometimes prevention of conditions where blood clots form in arteries, such as heart attack  and stroke.

Low-dose aspirin (meaning tablets containing 75-150 mg of aspirin) may be recommended on a daily basis for people who have already had a heart attack or stroke to prevent them from having another.

How does aspirin work?

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) work against pain by preventing prostaglandins from being made. Prostaglandins are chemical messengers the body produces which cause inflammation, pain, fever and swelling.

Aspirin stops pain-producing prostaglandins being made by inhibiting the enzyme cyclooxygenase (COX), which is involved in their production.

Another important effect of aspirin is to help prevent blood clots from forming in arteries. This anti-clotting effect of aspirin is achieved by reducing the stickiness of platelets in the blood, which impairs their ability to clump together and form a clot.

Aspirin for pain and fever

Aspirin can be used for the occasional treatment of mild to moderate pain and fever. It can be used as a painkiller for conditions such as headaches and migraines, period pain, toothache, cold and flu symptoms and joint and muscle pains.

Aspirin should not be given to children younger than 16 years, especially if the child also has symptoms of influenza or chickenpox or has fever. This is because aspirin can cause a serious and sometimes fatal condition in children called Reye’s syndrome (or Reye syndrome).

Aspirin for heart disease and stroke

A dose of aspirin is used by doctors as part of the initial emergency treatment for a heart attack.

Daily low-dose aspirin (between 100 and 150 mg/day) is recommended to prevent a second heart attack in people who have already had one unless a person is allergic to aspirin. The doctor may recommend that for the first 12 months, you take a combination aspirin and clopidogrel tablet.

Daily low-dose aspirin can also be taken to prevent stroke and transient ischaemic attacks (TIAs, or mini-strokes) in people who have had a previous stroke or TIA.

But the recommendations are different for people who have never had a heart attack or stroke. Current Australian guidelines do NOT recommend the use of daily low-dose aspirin to prevent cardiovascular disease in people with no past history of heart attack or stroke, including those thought to be at high risk.  This is because the risk of side effects outweighs the benefits for these people.

If someone has known coronary heart disease (including angina), then low-dose aspirin every day may be recommended to reduce the risk of heart attack.

Only take low-dose aspirin daily on the instructions of your doctor. You should always discuss with your doctor the risks and benefits of any medicines before taking them.

Side effects of aspirin

The majority of people don’t experience any side effects when taking aspirin; however, some people will suffer side effects.

The main side effects of aspirin happen when it irritates the stomach, causing heartburn, nausea or vomiting.

Because aspirin ‘thins’ your blood, making it harder to clot, taking aspirin can increase your risk of bleeding, including bleeding from the gastrointestinal tract. Bleeding from the stomach or gut is one of the most serious side effects of aspirin. For this reason, people with stomach or duodenal ulcers are usually advised not to take aspirin.

If you experience black tarry stools, or vomit blood or what looks coffee grounds, contact your doctor immediately.

Aspirin can cause an allergic reaction in some people, resulting in skin rash, hives, wheezing and difficulty breathing. The reaction usually happens within an hour of taking the aspirin. You should get immediate medical help if this happens to you or someone else.

In high doses, aspirin may cause ringing in the ears (tinnitus) or deafness.

Types of aspirin

Aspirin is usually taken by mouth. In Australia, there are different formulations of aspirin available including soluble tablets, chewable tablets, tablets and capsules. Aspirin is also available in combination products with other medicines, e.g. codeine, clopidogrel and dipyridamole.

Dosage of aspirin

When you are taking aspirin for fever, or the temporary relief of pain and inflammation, such as for headaches and period pain, the tablet strength is 300 mg or 500 mg.

‘Low-dose aspirin’ that is taken daily to prevent heart attack or stroke is a much lower dose than that given to relieve pain. The usual daily dose to prevent blood clots from forming in the arteries is one 100 mg tablet. Taking a larger dose than this will not protect you more, but will increase your risk of side effects.

You should take aspirin in the dose that is recommended for you and follow the instructions for use. Some types of aspirin should be taken with food to lessen stomach upset.

While aspirin is available over the counter, you shouldn’t take aspirin regularly without consulting your doctor.

Taking daily low-dose aspirin

As mentioned, daily low-dose aspirin is taken by many people with heart or blood vessel disease to reduce the risk of them having a heart attack or stroke. It does this by reducing the stickiness of platelets, which reduces the risk of blood clots forming in the arteries, which could lead to a heart attack or stroke.

Low-dose aspirin comes as:

  • tablets (e.g. Astrix tablets; Cardiprin 100 tablets); and
  • enteric-coated capsules or tablets (e.g. Astrix 100 capsules, Cartia tablets).

Enteric-coated aspirin resists being dissolved in the stomach regular aspirin and passes to the small intestine, where it is dissolved and enters the bloodstream.

This is supposed to help prevent the unwanted possible side effect of gastrointestinal bleeding and stomach ulcers.

However, as these risks may come from aspirin’s effect in the bloodstream, some doctors say there is no tangible advantage in taking enteric-coated aspirin.

If you are taking daily aspirin, it’s important that you don’t suddenly stop taking it as this could have a rebound effect and trigger a blood clot. Always talk to your doctor before stopping any regular medicines.

Low-dose aspirin may also be recommended for the prevention of pre-eclampsia in pregnancy, in women at increased risk.

Who should not take aspirin?

You should check with your doctor or pharmacist before taking aspirin, especially if you are taking any other regular medicines.

Taking aspirin when you are already taking other medicines to prevent clotting, such as warfarin, clopidogrel or heparin, can greatly increase your risk of bleeding.

The same applies if you are taking any of the newer anticoagulants – apixaban, dabigatran and rivaroxaban.

The following people should avoid using aspirin:

  • Anyone who has experienced an allergic reaction to aspirin or other non-steroidal anti-inflammatory medicines (NSAIDs), such as ibuprofen (e.g. Advil, Brufen, Nurofen), diclofenac (e.g. Voltaren), piroxicam (e.g. Feldene) and others.
  • People with asthma who have a history of asthma symptoms being triggered by aspirin or other NSAIDs.
  • Anyone with a recent history of a peptic ulcer (ulcer in the stomach or duodenum) or bleeding from the stomach or intestines.
  • People with haemophilia and other bleeding disorders.
  • People with severe liver or kidney disease.
  • Women who are pregnant or breastfeeding.
  • Children younger than 16 years should not take aspirin for pain relief or fever due to the risk of Reye’s syndrome, a serious condition.
  • People with gout should avoid taking daily low-dose aspirin.

People taking regular aspirin may need to stop taking aspirin 7-10 days before having any surgery or dental work to reduce the risk of bleeding. Your doctor or surgeon will be able to advise you on this.

Is aspirin safe in pregnancy?

Aspirin (and other NSAIDs) should be avoided in pregnancy, especially late pregnancy (the last 3 months) because they increase the risk of bleeding – both before birth and during delivery.

However, as mentioned, some women (who have a particular risk) may be prescribed low-dose regular aspirin to try to prevent pre-eclampsia.

Paracetamol is usually recommended for pain relief during pregnancy.

Can I take aspirin while breastfeeding?

No. It is not safe to take aspirin while breastfeeding unless prescribed by a doctor. Aspirin can pass into your breast milk, and there is a risk of Reye’s syndrome in your baby.


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