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Drugs reference index «Aspirin (Acetylsalicylic Acid; ASA)»


( Acetylsalicylic Acid ; ASA ) Pronunciation: (AS-pir-in)Class: Salicylate

Trade Names:Arthritis Foundation Pain Reliever- Tablets 500 mg

Trade Names:Bayer Children's Aspirin- Tablets, chewable 81 mg

Trade Names:Bayer Low Adult Strength- Tablets, delayed-release 81 mg

Trade Names:Easprin- Tablets, enteric-coated 975 mg

Trade Names:Ecotrin- Tablets, enteric-coated 81 mg- Tablets, enteric-coated 325 mg

Trade Names:Ecotrin Maximum Strength- Tablets, enteric-coated 500 mg

Trade Names:Empirin- Tablets 325 mg

Trade Names:Extended Release Bayer 8-Hour- Tablets, ER 650 mg

Trade Names:Extra Strength Bayer Enteric 500 Aspirin- Tablets, enteric-coated 500 mg

Trade Names:Genprin- Tablets 325 mg

Trade Names:Genuine Bayer- Tablets 325 mg

Trade Names:½ Halfprin- Tablets, enteric-coated 165 mg

Trade Names:Halfprin 81- Tablets, enteric-coated 81 mg

Trade Names:Heartline- Tablets, enteric-coated 81 mg

Trade Names:Maximum Bayer- Tablets 500 mg

Trade Names:Norwich Extra-Strength- Tablets 500 mg

Trade Names:Regular Strength Bayer Enteric Coated Caplets- Tablets, enteric-coated 325 mg

Trade Names:St. Joseph Adult Chewable Aspirin- Tablets, chewable 81 mg

Trade Names:ZORprin- Tablets, controlled-release 800 mg

Asaphen (Canada)Asaphen E.C. (Canada)Asatab (Canada)Coated Aspirin (Canada)Entrophen (Canada)


Inhibits prostaglandin synthesis, resulting in analgesia, anti-inflammatory activity, and platelet aggregation inhibition; reduces fever by acting on the brain's heat-regulating center to promote vasodilation and sweating.



Rapidly and completely absorbed. T max is 1 to 2 h (salicylic acid).


Widely distributed to all tissues and fluids, including CNS, breast milk, and fetal tissues. Approximately 90% of salicylate is protein bound at concentrations of less than 100 mcg/mL and approximately 75% is bound at concentrations of more than 400 mcg/mL.


Rapidly hydrolyzed to salicylic acid (active). Salicylic acid is conjugated in the liver to the metabolites.


Salicylic acid plasma half—life is approximately 6 h, but may exceed 20 h in higher doses. The half—life is approximately 15 to 20 min for aspirin. Elimination follows zero-order kinetics. Renal elimination of unchanged drug depends on urine pH. A pH of more than 6.5 increases renal Cl of free salicylate from less than 5% to more than 80%.

Indications and Usage

Treatment of mild to moderate pain; fever; various inflammatory conditions; reduction of risk of death or MI in patients with previous infarction or unstable angina pectoris, or recurrent transient ischemia attacks (TIAs) or stroke in men who have had transient brain ischemia caused by platelet emboli.

Unlabeled Uses

Prevention of cataract formation; prevention of toxemia of pregnancy; improvement of inadequate uteroplacental blood flow in pregnancy; prophylaxis against thromboembolic events in patients with atrial fibrillation, mitral valve prolapse, peripheral arterial disease, bioprosthetic or mechanical heart valves, and in pregnant patients with prosthetic heart valves; antithrombotic therapy in children with Blalock-Taussig shunt or ischemic stroke, and in children after Fontan surgery.


Hypersensitivity to salicylates or NSAIDs; hemophilia, bleeding ulcers, or hemorrhagic states.

Dosage and Administration

Acute MIAdults

PO 160 to 325 mg as soon as MI is suspected. Continue 160 to 325 mg daily for 30 days postinfarction. Consider further therapy after 30 days for prevention of recurrent MI. The American College of Chest Physicians recommends maintenance dosages of 75 to 100 mg once daily in patients post non–ST-segment elevation MI and 75 to 162 mg once daily in patients after ST-segment elevation MI.

Analgesic/AntipyreticAdults and Children 12 yr of age and older

PO 324 to 1,000 mg every 4 to 6 h as needed of regular-release products; max, 4,000 mg per 24 h. 1,300 mg followed by 650 to 1,300 mg every 8 h for controlled-release, delayed-release, or ER products; max, 3,900 mg per 24 h.

Children 2 to 12 yr of age

PO 10 to 15 mg/kg per dose every 4 h as needed (up to 80 mg/kg/day).

Angina PectorisAdults

PO 75 to 325 mg once daily.

Arthritis and Other Rheumatic ConditionsAdults

PO 3 g/day in divided doses.

Carotid EndarterectomyAdults

PO 80 mg once daily to 650 mg twice daily, started presurgery.

Coronary Artery Bypass GraftAdults

PO 325 mg daily starting 6 h postprocedure. Continue therapy for 1 yr postprocedure. The American College of Chest Physicians recommends 75 to 100 mg once daily, started 6 h after surgery.

Ischemic Stroke and TIAAdults

PO 50 to 325 mg once daily. The American College of Chest Physicians recommends 75 to 325 mg once daily in patients with cardioembolic stroke who have contraindications to anticoagulation and 50 to 100 mg once daily in patients with noncardioembolic stroke or TIA.

Juvenile Rheumatoid ArthritisChildren

PO 90 to 130 mg/kg/day in divided doses every 6 to 8 h.

MI ProphylaxisAdults

PO 75 to 325 mg/day. The American College of Chest Physicians recommends 75 to 100 mg once daily as primary prophylaxis.

Percutaneous Transluminal Coronary AngioplastyAdults

PO 325 mg 2 h presurgery, then 160 to 325 mg daily.


PO Up to 4 g/day in divided doses.

Off-Label DosingAtrial Fibrillation Adults

PO 75 to 325 mg once daily.

Bioprosthetic Aortic Valve Adults

PO 50 to 100 mg once daily.

Bioprosthetic Mitral Valve Adults

PO 50 to 100 mg once daily after 3 months of anticoagulation.

Blalock-Taussig Shunt, Fontan Surgery, or Ischemic Stroke Children

PO 1 to 5 mg/kg/day. Continue for a minimum of 2 yr in children with ischemic stroke.

Infrainguinal Arterial Reconstruction or Bypass Adults

PO 75 to 100 mg once daily, begun preoperatively.

Internal Mammary Artery Bypass Grafting Adults

PO 75 to 162 mg once daily.

Kawasaki Disease Adults

PO 80 to 100 mg/kg/day in 4 divided doses for up to 14 days within 10 days of symptom onset, followed by 1 to 5 mg/kg/day for a minimum of 6 to 8 wk. Aspirin therapy may continue indefinitely in patients with significant cardiac sequelae from Kawasaki disease.


PO 80 to 100 mg/kg/day in 4 divided doses until 48 to 72 h after fever defervescence, followed by 3 to 5 mg/kg/day. Continue for 6 to 8 weeks or until erythrocyte sedimentation rate and platelet count are normal and if no coronary artery abnormalities are present, or indefinitely if coronary artery abnormalities persist.

Mechanical Heart Valve Adults

PO 50 to 100 mg once a day in addition to anticoagulation.

Mitral Annular Calcification With Systemic Embolism, Stroke, or TIA Adults

PO 50 to 100 mg once daily

Mitral Valve Prolapse With Documented TIA or Stroke Adults

PO 50 to 100 mg once daily.

Postherpetic Neuralgia Adults

Topical Aspirin (median dose, 1,000 mg) in diethyl ether applied as a single dose. Other trials used multiple doses of different topical applications (1,200 mg in 20 to 30 mL of chloroform; 750 mg in 100 g of washable ointment).

Percutaneous Coronary Intervention (PCI) Adults

PO Initially, 300 to 325 mg between 2 and 24 h before PCI is performed in patients not on daily aspirin therapy, or 75 to 325 mg once before PCI is performed in patients on daily aspirin therapy. Follow by 162 to 325 mg once daily for 1, 3, and 6 months for patients with bare metal, sirolimus-eluting, and tacrolimus-eluting stents, respectively. Maintenance dosage is 75 to 162 mg.

Peripheral Arterial Disease Adults

PO 75 to 100 mg once daily.

Prophylaxis of Thromboembolism in Pregnant Women Prosthetic Heart Valves Adults

PO 75 to 100 mg once daily.


Store oral forms at room temperature in tightly closed containers.

Drug Interactions


May increase risk of GI ulceration and prolong bleeding time.

Antacids, corticosteroids, urinary alkalinizers

May decrease aspirin levels.

Carbonic anhydrase inhibitors (eg, acetohexamide), methotrexate, valproic acid

May increase levels of these drugs.

Heparin, oral anticoagulants

May increase risk of bleeding.

Insulin, sulfonylureas

Aspirin (more than 2 g/day) may potentiate glucose lowering.

Probenecid, sulfinpyrazone

May decrease uricosuric effect.

Laboratory Test Interactions

May increase levels of serum uric acid, cause false-positive readings of urine glucose by copper reduction method ( Clinitest ) and false-negative readings by glucose oxidase method ( Clinistix ); may interfere with urine tests of 5-hydroxyindoleacetic acid, ketone, phenolsulfonphthalein, vanillylmandelic acid.

Adverse Reactions


Dizziness; tinnitus.


Bleeding; dyspepsia; heartburn; nausea.


Anemia; decreased iron concentration; increased bleeding times.


Hypersensitivity reactions may include urticaria, hives, rashes, angioedema, and anaphylactic shock.



Category D .


Excreted in breast milk.


Reye syndrome has been associated with aspirin administration in children (including teenagers) with acute febrile illness.


Reaction may include bronchospasm and generalized urticaria or angioedema; patients with asthma or nasal polyps have greatest risk.

Renal Function

May decrease renal function or aggravate kidney diseases.

Hepatic Function

May cause hepatotoxicity in patients with impaired liver function.

GI disorders

Can cause gastric irritation and bleeding.

Surgical patients

Aspirin may increase risk of postoperative bleeding. If possible, avoid use 1 wk before surgery.



Convulsions, dizziness, hemorrhage, metabolic acidosis, nausea, respiratory alkalosis, tinnitus, vomiting.

Patient Information

  • Instruct patient to take drug with food or after meals and with full glass of water. Advise patient to avoid antacids within 1 to 2 h after ingestion of enteric-coated tablets.
  • Tell patient to discard any aspirin that has a vinegar-like odor.
  • Instruct patient to report ringing in ears or unusual bleeding, bruising, or persistent GI pain.
  • Advise patient on long-term therapy to inform health care provider or dentist before seeking surgery or dental care.
  • Tell patient on sodium-restricted diet to limit use of effervescent or buffered aspirin preparations.
  • Caution parents to avoid giving aspirin to children or teenagers with flu-like symptoms or chickenpox without first consulting health care provider.
  • Instruct patient to avoid intake of alcoholic beverages or other CNS depressants.

Copyright © 2009 Wolters Kluwer Health.

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