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 325 mg

Trade Names:

Ecotrin Adult Low Strength
- Tablets, enteric-coated 81 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


Inhibitors risk of renal impairment when aspirin (in doses over 300 mg daily) given with ACE inhibitors , also hypotensive effect antagonised
Angiotensin-II Receptor Antagonists risk of renal impairment when aspirin (in doses over 300 mg daily) given with angiotensin-II receptor antagonists , also hypotensive effect antagonised
Antacids excretion of aspirin increased by alkaline urine due to some antacids Antacids should preferably not be taken at the same time as other drugs since they may impair absorption
Antidepressants, SSRI increased risk of bleeding when aspirin given with SSRIs
Carbonic Anhydrase Inhibitors increased risk of toxicity when high-dose aspirin given with carbonic anhydrase inhibitors
Cilostazol manufacturer of cilostazol recommends dose of aspirin should not exceed 80 mg daily when given with cilostazol
Clopidogrel increased risk of bleeding when aspirin given with clopidogrel
Corticosteroids increased risk of gastro-intestinal bleeding and ulceration when aspirin given with corticosteroids , also corticosteroids reduce plasma concentration of salicylate Interactions do not generally apply to corticosteroids used for topical action (including inhalation) unless specified
Coumarins increased risk of bleeding when aspirin given with coumarins (due to antiplatelet effect) Change in patient's clinical condition, particularly associated with liver disease, intercurrent illness, or drug administration, necessitates more frequent testing. Major changes in diet (especially involving salads and vegetables) and in alcohol consumption may also affect anticoagulant control
Heparins aspirin enhances anticoagulant effect of heparins
Ibuprofen antiplatelet effect of aspirin possibly reduced by ibuprofen
Iloprost increased risk of bleeding when aspirin given with iloprost
Kaolin absorption of aspirin possibly reduced by kaolin
Methotrexate aspirin reduces excretion of methotrexate (increased risk of toxicity)—but for concomitant use in rheumatic disease see Methotrexate, section 10.1.3
Metoclopramide rate of absorption of aspirin increased by metoclopramide (enhanced effect)
Mifepristone avoidance of aspirin advised by manufacturer of mifepristone
NSAIDs avoid concomitant use of aspirin with NSAIDs (increased side-effects) See also Aspirin. Interactions do not generally apply to topical NSAIDs
Phenindione increased risk of bleeding when aspirin given with phenindione (due to antiplatelet effect) Change in patient's clinical condition particularly associated with liver disease, intercurrent illness, or drug administration, necessitates more frequent testing. Major changes in diet (especially involving salads and vegetables) and in alcohol consumption may also affect anticoagulant control
Phenytoin aspirin enhances effects of phenytoin
Probenecid aspirin antagonises effects of probenecid
Sibutramine increased risk of bleeding when aspirin given with sibutramine
Spironolactone aspirin antagonises diuretic effect of spironolactone
Sulfinpyrazone aspirin antagonises effects of sulfinpyrazone
Valproate aspirin enhances effects of valproate
Venlafaxine increased risk of bleeding when aspirin given with venlafaxine
Zafirlukast aspirin increases plasma concentration of zafirlukast
Aspirin belongs to Analgesics but Analgesics has no interactions information.


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.