Maximum Dose of Paracetamol IV
For adult patients, the maximum dose of intravenous paracetamol is 4 grams (4000 mg) per 24 hours, administered as either 650 mg IV every 4 hours or 1000 mg IV every 6 hours. 1
Standard IV Dosing Parameters
- Standard regimen: 650 mg IV every 4 hours OR 1000 mg IV every 6 hours 1
- Absolute maximum: 4 grams (4000 mg) per 24-hour period 1, 2
- Infusion rate: Each dose must be infused over at least 15 minutes (some sources recommend >30 minutes for higher doses) 1
Weight-Based Dosing for Patients <50 kg
For adults weighing less than 50 kg, the IV dose must be adjusted to 15 mg/kg every 4-6 hours, with a maximum of 60 mg/kg daily (not the standard 1 gram dose). 3
- Failure to adjust dosing in underweight patients is a common cause of iatrogenic paracetamol toxicity and potentially life-threatening acute liver failure 3
- Patient weight must be documented on the drug chart to prevent overdosing 3
- The standard 1 gram QDS (four times daily) dose applies only to patients ≥50 kg 3
High-Risk Populations Requiring Dose Reduction
Patients with cirrhosis or chronic liver disease: Maximum 2000-3000 mg per 24 hours 2, 4, 5
Elderly patients (≥60 years): Consider reducing maximum to 3000 mg per 24 hours, though single doses can remain at 1000 mg 5
Chronic alcohol users: Limit to 2000-3000 mg per 24 hours due to increased hepatotoxicity risk at doses ≤4000 mg 4, 5
Critical Safety Considerations for IV Administration
- Hypotension risk: IV paracetamol may cause hypotension in up to 50% of critically ill patients, which may preclude use in hemodynamically unstable patients 5
- Total daily intake: The 4 gram maximum includes ALL sources of paracetamol (IV, oral, rectal, and any combination products) 2, 5
- Monitoring: When used chronically or at maximum doses, monitor liver enzymes (AST/ALT) regularly 2
Common Pitfalls to Avoid
- Failing to weigh patients: Not documenting weight leads to inappropriate dosing in patients <50 kg 3
- Concurrent paracetamol sources: Not accounting for oral, rectal, or combination products when calculating total daily dose 2, 5
- Ignoring liver disease: Using standard 4 gram dosing in patients with cirrhosis or chronic alcohol use 2, 4
- Hemodynamic instability: Administering IV paracetamol to hypotensive patients without considering the risk of further blood pressure reduction 5
Conservative Dosing for Extended Use
For chronic daily use beyond acute management, limit to 3000 mg per 24 hours to minimize hepatotoxicity risk. 2, 5