Classification
Therapeutic: antipyretics, nonopioid analgesics
Indications
PO, Rect: Treatment of: Mild pain, Fever. IV: Treatment
of: Mild to moderate pain, Moderate to severe
pain with opioid analgesics, Fever.
Action
Inhibits synthesis of prostaglandins that may serve as
mediators of pain and fever, primarily in the CNS. Has
no significant anti-inflammatory properties or GI toxicity.
Therapeutic Effects: Analgesia. Antipyresis.
Pharmacokinetics
Absorption: Well absorbed following oral administration.
Rectal absorption is variable. Intravenous administration
results in complete bioavailability.
Distribution: Widely distributed. Crosses the placenta;
enters breast milk in low concentrations.
Metabolism and Excretion: 85–95% metabolized
by the liver (CYP2E1 enzyme system). Metabolites
may be toxic in overdose situation. Metabolites excreted
by the kidneys.
Half-life: Neonates: 7 hr; Infants and Children: 3–4
hr; Adults: 1–3 hr.
TIME/ACTION PROFILE (analgesia and
antipyresis)
ROUTE ONSET PEAK DURATION
PO 0.5–1 hr 1–3 hr 3–8 hr†
Rect 0.5–1 hr 1–3 hr 3–4 hr
IV‡ within 30 min 30 min 4–6 hr
†Depends on dose.
‡Antipyretic effects.
Contraindications/Precautions
Contraindicated in: Previous hypersensitivity;
Products containing alcohol, aspartame, saccharin,
sugar, or tartrazine (FDC yellow dye #5) should be
avoided in patients who have hypersensitivity or intolerance
to these compounds; Severe hepatic impairment/
active liver disease.
Use Cautiously in: Hepatic disease/renal disease
(lower chronic doses recommended); Alcoholism,
chronic malnutrition, severe hypovolemia or severe renal impairment (CCr 30 mL/min,qdosing interval
andpdaily dose may be necessary); Chronic alcohol
use/abuse; Malnutrition; OB: Use in pregnancy only if
clearly needed (for IV); Lactation: Use cautiously (for
IV).
Adverse Reactions/Side Effects
CNS: agitation (qin children) (IV), anxiety (IV),
headache (IV), fatigue (IV), insomnia (IV). Resp: atelectasis
(qin children) (IV), dyspnea (IV). CV: hypertension
(IV), hypotension (IV). GI: HEPATOTOXICITY
(qDOSES), constipation (qin children) (IV),qliver
enzymes, nausea (IV), vomiting (IV). F and E: hypokalemia
(IV). GU: renal failure (high doses/chronic
use). Hemat: neutropenia, pancytopenia. MS: muscle
spasms (IV), trismus (IV). Derm: ACUTE GENERALIZED
EXANTHEMATOUS PUSTULOSIS, STEVENS-JOHNSON SYNDROME,
TOXIC EPIDERMAL NECROLYSIS, rash, urticaria.
Interactions
Drug-Drug: Chronic high-dose acetaminophen (2
g/day) mayqrisk of bleeding with warfarin (INR
should not exceed 4). Hepatotoxicity is additive with
other hepatotoxic substances, including alcohol.
Concurrent use of isoniazid, rifampin, rifabutin,
phenytoin, barbiturates, and carbamazepine may
qthe risk of acetaminophen-induced liver damage
(limit self-medication); these agents will alsoptherapeutic
effects of acetaminophen. Concurrent use of
NSAIDs mayqthe risk of adverse renal effects (avoid
chronic concurrent use). Propranololpmetabolism
and mayqeffects. Maypeffects of lamotrigine and
zidovudine.
Route/Dosage
Children 12 yr should not receive 5 PO or rectal
doses/24 hr without notifying physician or other health
care professional. No dose adjustment needed when
converting between IV and PO acetaminophen in adults
and children 50 kg.
PO (Adults and Children 12 yr): 325–650 mg
every 6 hr or 1 g 3–4 times daily or 1300 mg every 8 hr
(not to exceed 3 g or 2 g/24 hr in patients with hepatic/
renal impairment).
PO (Children 1–12 yr): 10–15 mg/kg/dose every 6
hr as needed (not to exceed 5 doses/24 hr).
PO (Infants): 10–15 mg/kg/dose every 6 hr as
needed (not to exceed 5 doses/24 hr).
PO (Neonates): 10–15 mg/kg/dose every 6–8 hr as
needed.
IV (Adults and Children 13 yr and 50 kg):
1000 mg every 6 hr or 650 mg every 4 hr (not to exceed
1000 mg/dose, 4 g/day [by all routes], and less
than 4 hr dosing interval).
IV (Adults and Children 13 yr and 50 kg): 15
mg/kg every 6 hr or 12.5 mg/kg every 4 hr (not to exceed
15 mg/kg/dose [up to 750 mg/dose], 75 mg/kg/
day [up to 3750 mg/day] [by all routes], and less than
4 hr dosing interval).
IV (Children 2–12 yr): 15 mg/kg every 6 hr or 12.5
mg/kg every 4 hr (not to exceed 15 mg/kg/dose [up to 750 mg/dose], 75 mg/kg/day [up to 3750 mg/day] [by A
all routes], and less than 4 hr dosing interval).
IV (Infants 29 days-2 yr): 15 mg/kg every 6 hr (not
to exceed 60 mg/kg/day [by all routes]).
IV (Neonates Birth–28 days): 12.5 mg/kg every 6
hr (not to exceed 50 mg/kg [by all routes]).
Rect (Adults and Children 12 yr): 325–650 mg
every 4–6 hr as needed or 1 g 3–4 times/day (not to
exceed 4 g/24 hr).
Rect (Children 1–12 yr): 10–20 mg/kg/dose every
4–6 hr as needed.
Rect (Infants): 10–20 mg/kg/dose every 4–6 hr as
needed.
Rect (Neonates): 10–15 mg/kg/dose every 6–8 hr as
needed.
Availability (generic available)
Chewable tablets (fruit, bubblegum, or grape flavor):
80 mgOTC, 160 mgOTC. Tablets: 160 mgOTC, 325
mgOTC. Caplets: 325 mgOTC. Solution (berry, fruit,
and grape flavor): 100 mg/mLOTC. Liquid (mint):
160 mg/5 mLOTC. Elixir (grape and cherry flavor):
160 mg/5 mLOTC. Drops: 160 mg/ 5 mL OTC. Suspension:
100 mg/mLOTC, 160 mg/5 mLOTC. Syrup:
160 mg/5 mLOTC. Suppositories: 80 mgOTC, 120 mgOTC,
325 mgOTC. Solution for intravenous infusion: 1000
mg/100 mL in 100-mL vials. In combination with:
many other medications. See Appendix B.
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