What is the maximum single dose of paracetamol (acetaminophen) intravenous (IV) for a typical adult patient?

Maximum Single Dose of Paracetamol IV

The maximum single dose of intravenous paracetamol for a typical adult is 1000 mg (1 gram), administered every 4-6 hours, not exceeding 4000 mg in 24 hours. 1

Standard IV Dosing for Adults

• For adults weighing ≥50 kg: The single dose is 1000 mg every 4-6 hours 1
• The maximum daily dose is 4000 mg per 24 hours 1
• Each infusion should be administered over 15 minutes 2

Weight-Based Dosing for Adults <50 kg

• For adults weighing 10-50 kg: The dose must be reduced to 15 mg/kg every 4-6 hours (maximum 60 mg/kg daily) 3
• This is a critical safety consideration—failure to adjust dosing based on weight has resulted in iatrogenic paracetamol-induced hepatotoxicity 3
• Every patient should be weighed on admission, and the weight must be documented on the drug chart 3

High-Risk Populations Requiring Dose Reduction

Patients with Liver Disease

• Patients with cirrhosis or chronic liver disease should limit total daily intake to 2000-3000 mg 1
• The single dose can remain 1000 mg, but the dosing interval must be extended to stay within the reduced daily maximum 1

Elderly Patients (≥60 years)

• The single dose remains 1000 mg 1
• Consider reducing the maximum daily dose to 3000 mg for chronic use 1
• No routine dose reduction is required for short-term acute pain management in older adults without other risk factors 4

Chronic Alcohol Users

• Exercise extreme caution as hepatotoxicity can occur at lower doses 1
• Consider limiting to 2000-3000 mg daily maximum 5

Critical Safety Considerations

• Plasma concentrations after a 1-g IV dose range from approximately 35 mg/L (C_max) to 6 mg/L (C_min), well below toxic thresholds 2
• The toxic threshold is generally considered to be 150 mg/kg or ≥10 grams in a single acute ingestion 5
• Counsel patients to avoid all other paracetamol-containing products including over-the-counter cold remedies, sleep aids, and opioid combination products 1

Common Pitfalls to Avoid

• Failure to weigh patients on admission is the most common error leading to inappropriate dosing in patients <50 kg 3
• In one audit, 25% of patients on IV paracetamol were receiving inappropriate doses due to lack of weight documentation 3
• Even therapeutic doses of 4 g/day for 14 days can cause ALT elevations >3× normal in 31-41% of healthy adults, emphasizing the importance of adhering to maximum dosing limits 1

Hemodynamic Considerations

• IV paracetamol may cause hypotension, which may preclude its use in hemodynamically unstable patients 1
• Monitor blood pressure during and after infusion, particularly in critically ill patients 1