Maximum Recommended Dose of Intravenous Paracetamol
The maximum daily dose of intravenous paracetamol is 4000 mg per 24 hours in adults, administered as 1000 mg every 6 hours or 15 mg/kg every 6 hours (whichever is less), with a more conservative maximum of 3000 mg per day recommended for chronic use or high-risk populations. 1, 2
Standard Adult Dosing Parameters
For acute postoperative or emergency care, administer 1000 mg IV every 6 hours, not exceeding 4000 mg in 24 hours. 3, 1 The FDA has established this as the maximum daily therapeutic dose for healthy adults. 2
- A loading dose of 15-20 mg/kg (typically 1000-2000 mg) can be given initially, followed by maintenance doses of 10-15 mg/kg every 6-8 hours. 3
- The minimum interval between doses must be 4 hours, with a maximum of 6 doses in 24 hours. 1
- Single doses should not exceed 1000 mg. 1, 2
Conservative Dosing for Safety
For prolonged use beyond acute care (>48 hours), limit the maximum daily dose to 3000 mg to minimize hepatotoxicity risk. 1, 2 This recommendation comes from multiple sources including the National Comprehensive Cancer Network and represents a safer threshold for extended administration. 1
- Even therapeutic doses of 4000 mg/day for 14 days can cause ALT elevations >3× normal in 31-41% of healthy adults. 2, 4
- Repeated supratherapeutic ingestions (doses just above therapeutic range) carry worse prognosis than acute single overdoses, accounting for approximately 30% of acetaminophen overdose admissions. 1, 2
High-Risk Populations Requiring Dose Reduction
For patients with cirrhosis or chronic liver disease, reduce the maximum daily dose to 2000-3000 mg. 1, 2, 4
For elderly patients (≥60 years), reduce the maximum daily dose to 3000 mg per day. 1, 2
For chronic alcohol users, limit the maximum daily dose to 2000-3000 mg per day and counsel to avoid concurrent alcohol use. 1, 2 Severe hepatotoxicity has been documented with doses as low as 4-5 g/day in patients with chronic alcohol consumption, with mortality rates of 20-33%. 2, 4
Pediatric Dosing
For children, administer a loading dose of 15-20 mg/kg IV (10 mg/mL preparation), followed by 10-15 mg/kg every 6-8 hours, with a maximum daily dose of 60 mg/kg. 3
- For infants <10 kg, use 15 mg/kg for the loading dose. 3
Critical Safety Warnings
IV paracetamol may cause hypotension in up to 50% of critically ill patients, which may preclude use in hemodynamically unstable patients. 1 Monitor blood pressure closely during and after infusion.
When prescribing up to 4000 mg/day, explicitly counsel patients to avoid all other paracetamol-containing products including over-the-counter cold remedies, sleep aids, and opioid combination products. 1, 2 Prescription combination products are limited to ≤325 mg paracetamol per dosage unit by FDA mandate. 1, 2
Multimodal Analgesia Approach
When paracetamol alone provides insufficient pain control, add adjuvant therapies (NSAIDs, regional blocks, ketamine) rather than exceeding the 3000 mg daily maximum. 3, 1 Regular dosing of paracetamol up to 15 mg/kg every 6 hours (maximum 4 g per 24 hours) provides a good analgesic base in multimodal regimens. 3
- NSAIDs should be introduced postoperatively once renal function is confirmed normal and bleeding risk has passed. 3
- Low-dose ketamine (0.5 mg/kg IV followed by 1-2 μg/kg/min infusion) may be considered as an adjuvant in ICU patients. 1
Common Pitfalls to Avoid
Do not assume low or absent paracetamol levels rule out toxicity if ingestion was remote, occurred over several days, or timing is uncertain. 4 Very high aminotransferase levels (AST/ALT >3,500 IU/L) should raise suspicion of paracetamol poisoning even without clear overdose history. 4
Failing to recognize paracetamol in combination products leads to unintentional overdose. 1 Always verify all medications the patient is receiving contain no additional paracetamol sources.