Pharmacology
Acetaminophen Dosing
Patient Parameters
KG
US standard is 160mg/5mL. UK/AU often 120mg/5mL.
System Ready
Input patient weight and category to generate evidence-based dosing protocols.
Guidelines & Evidence
Verified
Last Review: 2026
When to Use
Primary Indications
Mild-to-moderate pain (headache, dental pain, musculoskeletal pain, dysmenorrhea)
Fever reduction (antipyretic) in adults and children
Postoperative pain (oral, rectal, or IV routes)
Severe pain: as an adjunct to opioid analgesics (reduces opioid requirements by 20-30%)
Osteoarthritis pain (first-line, especially when NSAIDs contraindicated)
Neonatal pain and fever (patent ductus arteriosus closure, post-circumcision)
Palliative care: chronic pain in patients with hepatic or renal impairment (with dose adjustment)
Clinical Utility
Acetaminophen is one of the most widely used over-the-counter analgesics globally. Unlike NSAIDs, it lacks anti-inflammatory effects and does not cause gastrointestinal bleeding, platelet dysfunction, or nephrotoxicity at therapeutic doses. Its safety profile makes it first-line for pain/fever in children, pregnancy (ACOG considers safe), breastfeeding, and patients with bleeding diatheses or NSAID hypersensitivity. The IV formulation (Ofirmev) provides rapid onset (peak 15-30 min) and is used in hospital settings for postoperative pain when oral intake is restricted. However, clinical evidence shows IV acetaminophen offers limited benefit over oral/rectal routes in most surgical settings.
Comparison with Other Analgesics
| Agent | Analgesic | Antipyretic | Anti-inflammatory | GI Bleeding Risk | Platelet Effect | Nephrotoxicity | Hepatotoxicity Risk | Pregnancy Safety |
|---|---|---|---|---|---|---|---|---|
| Acetaminophen | ✓✓ | ✓✓ | ✗ | None | None | Minimal (chronic high dose) | Yes (overdose) | Yes (ACOG) |
| Ibuprofen (NSAID) | ✓✓ | ✓✓ | ✓✓ | Moderate | Reversible inhibition | Chronic use risk | Minimal | Caution (3rd trimester) |
| Naproxen (NSAID) | ✓✓ | ✓✓ | ✓✓✓ | Moderate-High | Reversible inhibition | Chronic use risk | Minimal | Caution (3rd trimester) |
| Aspirin | ✓ | ✓✓ | ✓✓ | High | Irreversible inhibition | Yes (analgesic nephropathy) | Minimal (Reye risk in children) | Avoid (3rd trimester) |
| Opioids (e.g., tramadol) | ✓✓✓ | ✗ | ✗ | Constipation (no bleeding) | None | None | None (except combination products) | Variable, caution |
Last Comprehensive Review: 2026