acetaminophen (N-acetyl-p-aminophenol)

acetaminophen (N-acetyl-p-aminophenol)

(a seet a min' a fen)

Suppositories:

Abenol (CAN), Acephen

Oral:

Aceta, Apacet, Atasol (CAN), Genapap, Genebs, Liquiprin, Mapap, Panadol, Tapanol, Tempra, Tylenol

Pregnancy Category B

Drug classes

Antipyretic

Analgesic (nonopioid)

Therapeutic actions

Antipyretic: Reduces fever by acting directly on the hypothalamic heat-regulating center to cause vasodilation and sweating, which helps dissipate heat.

Analgesic: Site and mechanism of action unclear.

Indications

·        Analgesic-antipyretic in patients with aspirin allergy, hemostatic disturbances, bleeding diatheses, upper GI disease, gouty arthritis

·        Arthritis and rheumatic disorders involving musculoskeletal pain (but lacks clinically significant antirheumatic and anti-inflammatory effects)

·        Common cold, flu, other viral and bacterial infections with pain and fever

·        Unlabeled use: Prophylactic for children receiving DPT vaccination to reduce incidence of fever and pain

Contraindications and cautions

·        Contraindicated with allergy to acetaminophen.

·        Use cautiously with impaired hepatic function, chronic alcoholism, pregnancy, lactation.

Available forms

Suppositories—80, 120, 125, 300, 325, 650 mg; chewable tablets—80 mg; tablets—160, 325, 500, 650 mg; caplets—160, 500, 650 mg; gelcaps—500 mg; capsules—325, 500 mg; elixir—80 mg/2.5 mL, 80 mg/5 mL, 120 mg/5 mL, 160 mg/5 mL; liquid—160 mg/5 mL, 500 mg/15 mL; solution—80 mg/1.66 mL, 100 mg/mL; drops—80 mg/0.8 mL; sprinkle capsules—80, 160 mg

Dosages

ADULTS

PO or PR

By suppository, 325–650 mg q 4–6 hr or PO, 1,000 mg tid to qid. Do not exceed 4 g/day.

PEDIATRIC PATIENTS

PO or PR

Doses may be repeated 4–5 times/day; do not exceed five doses in 24 hr; give PO or by suppository.

Age	Dosage (mg)
0–3 mo	40
4–11 mo	80
12–23 mo	120
2–3 yr	160
4–5 yr	240
6–8 yr	320
9–10 yr	400
11 yr	480

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	Varies	0.5–2 hr	3–4 hr

Metabolism: Hepatic; T_1/2: 1–3 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

Adverse effects

·        CNS: Headache

·        CV: Chest pain, dyspnea, myocardial damage when doses of 5–8 g/day are ingested daily for several weeks or when doses of 4 g/day are ingested for 1 yr

·        GI: Hepatic toxicity and failure, jaundice

·        GU: Acute kidney failure, renal tubular necrosis

·        Hematologic: Methemoglobinemia—cyanosis; hemolytic anemia—hematuria, anuria; neutropenia, leukopenia, pancytopenia, thrombocytopenia, hypoglycemia

·        Hypersensitivity: Rash, fever

Interactions

Drug-drug

·        Increased toxicity with long-term, excessive ethanol ingestion

·        Increased hypoprothrombinemic effect of oral anticoagulants

·        Increased risk of hepatotoxicity and possible decreased therapeutic effects with barbiturates, carbamazepine, hydantoins, rifampin, sulfinpyrazone

·        Possible delayed or decreased effectiveness with anticholinergics

·        Possible reduced absorption of acetaminophen with activated charcoal

·        Possible decreased effectiveness of zidovudine

Drug-lab test

·        Interference with Chemstrip G, Dextrostix, Visidex II home blood glucose measurement systems; effects vary

Nursing considerations

Assessment

·        History: Allergy to acetaminophen, impaired hepatic function, chronic alcoholism, pregnancy, lactation

·        Physical: Skin color, lesions; T; liver evaluation; CBC, LFTs, renal function tests

Interventions

·        Do not exceed the recommended dosage.

·        Consult physician if needed for children < 3 yr; if needed for longer than 10 days; if continued fever, severe or recurrent pain occurs (possible serious illness).

·        Avoid using multiple preparations containing acetaminophen. Carefully check all OTC products.

·        Give drug with food if GI upset occurs.

·        Discontinue drug if hypersensitivity reactions occur.

·        Treatment of overdose: Monitor serum levels regularly, N-acetylcysteine should be available as a specific antidote; basic life support measures may be necessary.

Teaching points

·        Do not exceed recommended dose; do not take for longer than 10 days.

·        Take the drug only for complaints indicated; it is not an anti-inflammatory agent.

·        Avoid the use of other over-the-counter preparations. They may contain acetaminophen, and serious overdosage can occur. If you need an over-the-counter preparation, consult your health care provider.

·        Report rash, unusual bleeding or bruising, yellowing of skin or eyes, changes in voiding patterns.

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