What is the recommended paracetamol dose per kilogram for an adult and the maximum total daily dose?

Paracetamol (Acetaminophen) Dosing in Adults

For healthy adults, the standard dose is 650-1000 mg every 4-6 hours, with a maximum daily limit of 4000 mg per 24 hours, though limiting to 3000 mg daily for chronic use significantly reduces hepatotoxicity risk. 1

Standard Dosing Parameters

• Single dose: 650-1000 mg, with 1000 mg being the maximum per dose 1
• Dosing interval: Every 4-6 hours, with a minimum 4-hour interval between doses 1, 2
• Maximum daily dose: 4000 mg per 24 hours (maximum 6 doses) 1, 3
• Weight-based dosing: 15 mg/kg per dose for adults weighing 10-50 kg (particularly for IV administration), not exceeding 60 mg/kg daily 4

The FDA established this 4000 mg maximum through the monograph process, though this limit is currently under evaluation due to hepatotoxicity concerns 1, 5.

Conservative Dosing for Safety (Strongly Recommended)

For any use beyond acute care or lasting more than a few days, limit the maximum to 3000 mg daily. 1, 3

This conservative approach is critical because:

• Even therapeutic doses of 4000 mg/day for just 14 days cause liver enzyme elevations (ALT >3× normal) in 31-41% of healthy adults 1
• The National Comprehensive Cancer Network specifically recommends the 3000 mg daily maximum to minimize hepatotoxicity risk 1, 3
• Repeated supratherapeutic ingestions (even slightly above recommended doses over days) carry worse prognosis than acute single overdoses, accounting for 30% of acetaminophen overdose admissions 1, 3

High-Risk Populations Requiring Mandatory Dose Reduction

Patients with Liver Disease

• Maximum: 2000-3000 mg daily for cirrhosis or chronic liver disease 1, 3
• Paracetamol can be used in compensated cirrhosis but requires individualized dosing in decompensated disease 6

Chronic Alcohol Users

• Maximum: 2000-3000 mg daily 2, 3
• Hepatotoxicity can occur at doses ≤4000 mg, with severe liver damage documented at 5-8.75 g/day in chronic alcohol users 1
• The American College of Emergency Physicians confirms increased hepatotoxicity risk at lower doses in this population 1

Elderly Patients (≥60 years)

• Maximum: 3000 mg daily, though single doses remain 1000 mg 1, 3
• No evidence supports routine dose reduction below 3000 mg daily in otherwise healthy older adults 6

Patients <50 kg Body Weight

• Dose: 15 mg/kg per dose (not the standard 1000 mg), maximum 60 mg/kg daily 4
• This is particularly critical for IV administration where failure to adjust has caused iatrogenic hepatotoxicity 4

Critical Safety Warnings

Hidden Paracetamol Sources

When prescribing up to 4000 mg/day, explicitly counsel patients to avoid ALL other paracetamol-containing products including: 1, 3

• Over-the-counter cold and flu remedies
• Sleep aids
• Prescription opioid combination products (codeine/paracetamol, tramadol/paracetamol)

The FDA mandates that prescription combinations contain ≤325 mg paracetamol per unit specifically to reduce inadvertent overdose risk 1.

Hepatotoxicity Recognition

• AST >1000 IU/L indicates developing toxicity 1
• Very high aminotransferase levels should raise suspicion even without clear overdose history 3
• Chronic exposures >140 mg/kg/day for several days carry serious toxicity risk 2, 7

Route-Specific Considerations

Intravenous Administration

• Loading dose: 15-20 mg/kg, followed by 10-15 mg/kg every 6-8 hours 3
• Standard adult dose: 1000 mg IV every 6 hours, maximum 4000 mg/24 hours 3
• Warning: IV paracetamol causes hypotension in up to 50% of critically ill patients, potentially precluding use in hemodynamically unstable patients 3

Oral Administration

• Effervescent tablets provide more rapid absorption and onset than conventional tablets, though serum concentrations don't directly correlate with analgesic effect 8
• Bioavailability is linear at therapeutic concentrations and constant with repeated administration 8

Common Pitfalls to Avoid

1. Failing to weigh patients: Every patient should be weighed on admission, with weight documented on drug charts to enable proper dose adjustment for those <50 kg 4

2. Assuming absence of toxicity from low paracetamol levels: Low or absent levels don't rule out toxicity if ingestion was remote, occurred over several days, or timing is uncertain 3

3. Not recognizing combination products: Verify patients are not receiving paracetamol from multiple sources simultaneously 3

4. Exceeding daily maximums to achieve pain control: When 3000 mg daily provides insufficient analgesia, add adjuvant therapies (NSAIDs, regional blocks, ketamine) rather than exceeding the safe maximum 3

Multimodal Analgesia Approach

When paracetamol alone is insufficient: 3

• Add NSAIDs (once renal function confirmed and bleeding risk passed)
• Consider regional nerve blocks (TAP blocks, epidural, rectus sheath blocks)
• Low-dose ketamine as adjuvant in ICU patients
• Regular paracetamol dosing (15 mg/kg every 6 hours) provides good analgesic base for multimodal regimens