Acetaminophen
Brand names: Tylenol, APAP, Paracetamol
Class: 🤕 NSAIDs & Analgesics
The AANP exam tests acetaminophen as the safe analgesic that becomes dangerous at the wrong dose. It is the first choice for mild-to-moderate pain or fever in patients with CKD, heart failure, peptic ulcer disease, anticoagulation, or third-trimester pregnancy — situations where NSAIDs are unsafe. There is no anti-inflammatory effect. The dose ceiling is 3–4 g/day in healthy adults and 2 g/day in chronic alcohol use, malnutrition, or hepatic impairment. Hepatotoxicity is the dose-limiting harm; N-acetylcysteine reverses overdose if started early. Watch for hidden acetaminophen in combination cold remedies and Percocet — the cumulative dose is what trips up real patients and exam takers.
✅ Indications
Mild-moderate pain, fever. First-line in CKD, CHF, peptic ulcer, anticoagulated patients.
⚙️ Mechanism of Action
Central COX inhibition (exact mechanism unclear); minimal anti-inflammatory effect.
📏 Dosing
Adults: 325–1000 mg q4–6h. Max 4 g/day (3 g if chronic alcohol, hepatic impairment, elderly).
🚫 Contraindications
Severe hepatic impairment, alcohol abuse (caution).
⚠️ Adverse Effects
HEPATOTOXICITY (dose-dependent, centrilobular necrosis), rare SJS/TEN.
🔬 Monitoring
LFTs if concern; chronic use check.
💎 Board Pearls
- 🍺 MAX 4 g/day healthy adult; 3 g/day for chronic EtOH, hepatic impairment, or frail elderly.
- 🆘 Overdose antidote: N-acetylcysteine (NAC). Give within 8–10 hours for best outcome; still helpful up to 24h.
- 🤰 SAFE in pregnancy — first-line.
- 💊 NO anti-inflammatory effect — not useful for inflammatory pain (go ibuprofen for those).
Practice Questions
A 27-year-old woman at 24 weeks gestation reports a tension-type headache. Which analgesic is the first-line choice during pregnancy?
Related Drugs in This Class
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