A-Z Drug Facts > Aspirin (Acetylsalicylic Acid; ASA)

Aspirin

( Acetylsalicylic Acid ; ASA ) Pronunciation: (ASS-pihr-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, extended-release 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)

Pharmacology

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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.

Pharmacokinetics

Absorption

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

Distribution

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.

Metabolism

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

Elimination

Salicylic acid plasma t _½ is approximately 6 h but may exceed 20 h in higher doses. The t _½ 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 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.

Contraindications

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

Dosage and Administration

Analgesic/Antipyretic
Adults

PO 325 to 650 mg every 4 h as needed; 500 mg every 3 h as needed; 1,000 mg every 6 h as needed.

Children (2 to 12 yr of age)

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

Arthritis and Other Rheumatic Conditions
Adults

PO 3.2 to 6 g/day in divided doses.

Juvenile Rheumatoid Arthritis
Children

PO 60 to 110 mg/kg/day in divided doses every 6 to 8 h.

Acute Rheumatic Fever
Adults

PO 5 to 8 g/day, initially, for up to 2 wk. Subsequent doses are based on patient response.

Children

PO 75 to 100 mg/kg/day.

Transient Ischemic Attacks in Men
Adults

PO 1300 mg/day in 2 to 4 doses.

MI Prophylaxis
Adults

PO 160 to 325 mg/day.

Kawasaki Disease
Children

PO 80 to 180 mg/kg/day during acute febrile period; 10 mg/kg/day after fever resolves.

Storage/Stability

Store oral forms at room temperature in tightly closed container.

Drug Interactions

Alcohol

May increase risk of GI ulceration and prolong bleeding time.

Antacids, urinary alkalinizers, and corticosteroids

May decrease aspirin levels.

Anticoagulants, oral and heparin

May increase risk of bleeding.

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

May increase levels of these drugs.

Probenecid, sulfinpyrazone

May decrease uricosuric effect.

Sulfonylureas, insulin

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

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

EENT

Dizziness; tinnitus.

GI

Nausea; dyspepsia; heartburn; bleeding.

Hematologic

Increased bleeding times; anemia; decreased iron concentration.

Miscellaneous

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

Precautions

Pregnancy

Category D .

Lactation

Excreted in breast milk.

Children

Reye syndrome has been associated with aspirin administration to children (including teenagers) with acute febrile illness. Do not use without consulting health care provider.

Hypersensitivity

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.

Overdosage

Symptoms

Nausea, vomiting, tinnitus, dizziness, respiratory alkalosis, metabolic acidosis, hemorrhage, convulsions.

Patient Information

• Instruct patient to take drug with food or after meals and with full glass of water. Explain that antacids should be avoided 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.

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