Aspirin

aspirin

(ass' pir in)

Apo-ASA (CAN), Aspergum, Bayer, Easprin, Ecotrin, Empirin, Entrophen (CAN), Genprin, Halfprin 81, 1/2 Halfprin, Heartline, Norwich, Novasen (CAN), PMS-ASA (CAN), ZORprin

Buffered aspirin products:

Alka-Seltzer, Ascriptin, Asprimox, Bufferin, Buffex, Magnaprin

Pregnancy Category D

Drug classes

Antipyretic

Analgesic (nonopioid)

Anti-inflammatory

Antirheumatic

Antiplatelet

Salicylate

NSAID

Therapeutic actions

Analgesic and antirheumatic effects are attributable to aspirin's ability to inhibit the synthesis of prostaglandins, important mediators of inflammation. Antipyretic effects are not fully understood, but aspirin probably acts in the thermoregulatory center of the hypothalamus to block effects of endogenous pyrogen by inhibiting synthesis of the prostaglandin intermediary. Inhibition of platelet aggregation is attributable to the inhibition of platelet synthesis of thromboxane A₂, a potent vasoconstrictor and inducer of platelet aggregation. This effect occurs at low doses and lasts for the life of the platelet (8 days). Higher doses inhibit the synthesis of prostacyclin, a potent vasodilator and inhibitor of platelet aggregation.

Indications

·        Mild to moderate pain

·        Fever

·        Inflammatory conditions—rheumatic fever, rheumatoid arthritis, osteoarthritis

·        Reduction of risk of recurrent TIAs or stroke in males with history of TIA due to fibrin platelet emboli

·        Reduction of risk of death or nonfatal MI in patients with history of infarction or unstable angina pectoris

·        MI prophylaxis

·        Unlabeled use: Prophylaxis against cataract formation with long-term use

Contraindications and cautions

·        Contraindicated with allergy to salicylates or NSAIDs (more common with nasal polyps, asthma, chronic urticaria); allergy to tartrazine (cross-sensitivity to aspirin is common); hemophilia, bleeding ulcers, hemorrhagic states, blood coagulation defects, hypoprothrombinemia, vitamin K deficiency (increased risk of bleeding)

·        Use cautiously with impaired renal function; chickenpox, influenza (risk of Reye's syndrome in children and teenagers); children with fever accompanied by dehydration; surgery scheduled within 1 wk; pregnancy (maternal anemia, antepartal and postpartal hemorrhage, prolonged gestation, and prolonged labor have been reported; readily crosses the placenta; possibly teratogenic; maternal ingestion of aspirin during late pregnancy has been associated with the following adverse fetal effects: low birth weight, increased intracranial hemorrhage, stillbirths, neonatal death); lactation.

Available forms

Tablets—81, 165, 325, 500, 650, 975 mg; SR tablets—650, 800 mg; suppositories—120, 200, 300, 600 mg

Dosages

Available in oral and suppository forms. Also available as chewable tablets, gum; enteric coated, SR, and buffered preparations (SR aspirin is not recommended for antipyresis, short-term analgesia, or children < 12 yr.)

ADULTS

·        Minor aches and pains: 325–650 mg q 4 hr.

·        Arthritis and rheumatic conditions: 3.2–6 g/day in divided doses.

·        Acute rheumatic fever: 5–8 g/day; modify to maintain serum salicylate level of 15–30 mg/dL.

·        TIAs in men:1,300 mg/day in divided doses (650 mg bid or 325 mg qid).

·        MI prophylaxis: 75–325 mg/day.

PEDIATRIC PATIENTS

·        Analgesic and antipyretic: 65 mg/kg per 24 hr in four to six divided doses, not to exceed 3.6 g/day. Dosage recommendations by age:

Age (yr)	Dosage (mg q 4 hr)
2–3	162
4–5	243
6–8	324
9–10	405
11	486
³ 12	648

·        Juvenile rheumatoid arthritis: 60–110 mg/kg per 24 hr in divided doses at 6- to 8-hr intervals. Maintain a serum level of 150–300 mcg/mL.

·        Acute rheumatic fever: Initially, 100 mg/kg/day, then decrease to 75 mg/kg/day for 4–6 wk. Therapeutic serum salicylate level is 150–300 mg/dL.

·        Kawasaki disease: 80–180 mg/kg/day; very high doses may be needed during acute febrile period; after fever resolves, dosage may be adjusted to 10 mg/kg/day.

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	5–30 min	15–120 min	3–6 hr
Rectal	1–2 hr	4–5 hr	6–8 hr

Metabolism: Hepatic (salicylate); T_1/2: 15 min–12 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

Adverse effects

·        Acute aspirin toxicity: Respiratory alkalosis, hyperpnea, tachypnea, hemorrhage, excitement, confusion, asterixis, pulmonary edema, seizures, tetany, metabolic acidosis, fever, coma, CV collapse, renal and respiratory failure (dose related, 20–25 g in adults, 4 g in children)

·        Aspirin intolerance: Exacerbation of bronchospasm, rhinitis (with nasal polyps, asthma, rhinitis)

·        GI: Nausea, dyspepsia, heartburn, epigastric discomfort, anorexia, hepatotoxicity

·        Hematologic: Occult blood loss, hemostatic defects

·        Hypersensitivity: Anaphylactoid reactions to anaphylactic shock

·        Salicylism: Dizziness, tinnitus, difficulty hearing, nausea, vomiting, diarrhea, mental confusion, lassitude (dose related)

Interactions

Drug-drug

·        Increased risk of bleeding with oral anticoagulants, heparin

·        Increased risk of GI ulceration with steroids, phenylbutazone, alcohol, NSAIDs

·        Increased serum salicylate levels due to decreased salicylate excretion with urine acidifiers (ammonium chloride, ascorbic acid, methionine)

·        Increased risk of salicylate toxicity with carbonic anhydrase inhibitors, furosemide

·        Decreased serum salicylate levels with corticosteroids

·        Decreased serum salicylate levels due to increased renal excretion of salicylates with acetazolamide, methazolamide, certain antacids, alkalinizers

·        Decreased absorption of aspirin with nonabsorbable antacids

·        Increased methotrexate levels and toxicity with aspirin

·        Increased effects of valproic acid secondary to displacement from plasma protein sites

·        Greater glucose lowering effect of sulfonylureas, insulin with large doses (> 2 g/day) of aspirin

·        Decreased antihypertensive effect of captopril, beta-adrenergic blockers with salicylates; consider discontinuation of aspirin

·        Decreased uricosuric effect of probenecid, sulfinpyrazone

·        Possible decreased diuretic effects of spironolactone, furosemide (in patients with compromised renal function)

·        Unexpected hypotension may occur with nitroglycerin

Drug-lab test

·        Decreased serum protein bound iodine (PBI) due to competition for binding sites

·        False-negative readings for urine glucose by glucose oxidase method and copper reduction method with moderate to large doses of aspirin

·        Interference with urine 5-HIAA determinations by fluorescent methods but not by nitrosonaphthol colorimetric method

·        Interference with urinary ketone determination by the ferric chloride method

·        Falsely elevated urine VMA levels with most tests; a false decrease in VMA using the Pisano method

Nursing considerations

Assessment

·        History: Allergy to salicylates or NSAIDs; allergy to tartrazine; hemophilia, bleeding ulcers, hemorrhagic states, blood coagulation defects, hypoprothrombinemia, vitamin K deficiency; impaired hepatic function; impaired renal function; chickenpox, influenza; children with fever accompanied by dehydration; surgery scheduled within 1 wk; pregnancy; lactation

·        Physical: Skin color, lesions; T; eighth cranial nerve function, orientation, reflexes, affect; P, BP, perfusion; R, adventitious sounds; liver evaluation, bowel sounds; CBC, clotting times, urinalysis, stool guaiac, LFTs, renal function tests

Interventions

·        Give drug with food or after meals if GI upset occurs.

·        Give drug with full glass of water to reduce risk of tablet or capsule lodging in the esophagus.

·        Do not crush, and ensure that patient does not chew SR preparations.

·        Do not use aspirin that has a strong vinegar-like odor.

·        WARNING: Institute emergency procedures if overdose occurs: Gastric lavage, induction of emesis, activated charcoal, supportive therapy.

Teaching points

·        Take extra precautions to keep this drug out of the reach of children; this drug can be very dangerous for children.

·        Use the drug only as suggested; avoid overdose. Avoid the use of other over-the-counter drugs while taking this drug. Many of these drugs contain aspirin, and serious overdose can occur.

·        Take the drug with food or after meals if GI upset occurs.

·        Do not cut, crush, or chew sustained-release products.

·        Over-the-counter aspirins are equivalent. Price does not reflect effectiveness.

·        You may experience these side effects: Nausea, GI upset, heartburn (take drug with food); easy bruising, gum bleeding (related to aspirin's effects on blood clotting).

·        Report ringing in the ears; dizziness, confusion; abdominal pain; rapid or difficult breathing; nausea, vomiting, bloody stools.

Adverse effects in Italic are most common; those in Bold are life-threatening.