Acetaminophen: Difference between revisions
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== References == | == References == | ||
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[[Category:Analgesics]] | |||
[[Category:Antipyretics]] | |||
Latest revision as of 10:43, 23 May 2026
Acetaminophen (paracetamol, APAP)
Tylenol, Panadol (international), Ofirmev (IV); huge OTC presence
Experience
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Effects
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Summary
Classes
Common uses
Mild to moderate pain0, Fever0, Multimodal post-surgical analgesia0
Pharmacy
Starting dose
325-1000 mg PO every 4-6 hours as needed; maximum 4 g/d in healthy adults, 3 g/d in regular users or hepatic risk; pediatric 10-15 mg/kg every 4-6 hours
Preparations
325, 500, 650 mg tablets; 80, 160 mg chewables; 160 mg/5 mL pediatric liquid; 325 mg suppository; 1000 mg/100 mL IV (Ofirmev); fixed-dose combinations with opioids, decongestants, antihistamines
US FDA Max
4 g/d in healthy adults; 3 g/d conservative limit; 2 g/d in cirrhosis or chronic alcohol use
Pharmacology
Routes
Oral, rectal, IV
Onset
PO: 30-60 minutes; IV: minutes
Duration
4-6 hours
Half-life
1-3 hours (normal liver); markedly prolonged in overdose with glutathione depletion[1]
Bioavailability
~85-98% (oral)[1]
Pregnancy
Long the preferred analgesic-antipyretic in pregnancy; recent observational studies have raised speculative neurodevelopmental signals that remain under investigation.[citation needed]
Legal status
OTC and Rx-only (IV, combination products) in US
Purported mechanism
Acetaminophen's analgesic and antipyretic actions are incompletely characterized; central COX inhibition (particularly the COX-2 splice variant sometimes called COX-3, and inhibition of arachidonic acid pathways in CNS at low peroxide concentrations) is the leading hypothesis, with possible contribution from descending serotonergic pathways and TRPV1 modulation by the AM404 metabolite.0 The absence of meaningful peripheral cyclooxygenase inhibition explains the lack of antiplatelet and anti-inflammatory effect compared with NSAIDs, and the gastroprotective profile. Dose-dependent hepatotoxicity via the CYP2E1 metabolite N-acetyl-p-benzoquinone imine (NAPQI) once glutathione is depleted; N-acetylcysteine is the antidote and is most effective within 8-10 hours of overdose[1].
References
- ↑ 1.0 1.1 1.2 FDA OTC Monograph for acetaminophen-containing products, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/021450s015lbl.pdf