Can I give a 1000 mg dose of paracetamol (acetaminophen) to a 17‑year‑old patient weighing 37 kg?

Paracetamol 1000 mg IV Dosing for 37 kg, 17-Year-Old Patient

No, you should not give 1000 mg paracetamol IV to a 37 kg patient—this dose is too high and carries significant hepatotoxicity risk. The appropriate dose for this patient is 555 mg (15 mg/kg), not to exceed 750 mg per dose.

Weight-Based Dosing Requirements

For patients weighing less than 50 kg, paracetamol dosing must be calculated by weight, not given as standard adult doses. 1

• Loading dose: 15-20 mg/kg IV initially 1
• Maintenance doses: 10-15 mg/kg every 6-8 hours 1
• For this 37 kg patient: 555 mg (15 mg/kg) per dose is appropriate 1
• Maximum single dose for <50 kg patients: Should not exceed 15 mg/kg 1

The 1000 mg dose you're considering represents 27 mg/kg for this patient—nearly double the recommended maximum single dose and well into the potentially toxic range. 1

Why This Matters: Toxicity Thresholds

A 1000 mg dose in a 37 kg patient approaches supratherapeutic levels that have caused severe hepatotoxicity. 2

• Repeated doses of ≥150 mg/kg per 24-hour period for 48 hours or longer are potentially toxic 2
• If you gave 1000 mg every 6 hours (standard adult dosing), this patient would receive 108 mg/kg/day—approaching the 150 mg/kg threshold for repeated supratherapeutic ingestion 2
• Severe hepatotoxicity has been documented with chronic exposures greater than 140 mg/kg/day for several days 3
• Even therapeutic doses of 4 g/day for 14 days caused ALT elevations >3 times normal in 31-41% of healthy adults 2

Correct Dosing Algorithm for This Patient

Step 1: Calculate weight-based dose

• 37 kg × 15 mg/kg = 555 mg per dose 1
• Round to practical volume based on your IV paracetamol concentration

Step 2: Establish dosing interval

• Administer every 6-8 hours 1
• Minimum 4-hour interval between doses 1
• Maximum 6 doses in 24 hours 1

Step 3: Calculate maximum daily dose

• Maximum: 60 mg/kg/day for pediatric/adolescent patients 1, 3
• For this 37 kg patient: 2,220 mg/day maximum 3
• This is approximately four 555 mg doses per day (2,220 mg total)

Step 4: Monitor for toxicity

• Watch for any signs of hepatotoxicity (elevated transaminases) 2
• Consider baseline and follow-up liver function tests if prolonged use anticipated 2

Critical Pitfall to Avoid

The most dangerous error is applying standard adult dosing (1000 mg) to patients <50 kg. 1 This is a common mistake in emergency and perioperative settings where providers default to "1 gram IV paracetamol" without weight-based calculation.

• Adult dosing of 1000 mg every 6 hours assumes a patient weight of approximately 67-100 kg 1
• For a 37 kg patient, this represents massive overdosing that accumulates with each dose 2
• The FDA label for oral paracetamol specifies that children 12 years and over receive 650 mg (not 1000 mg) every 4-6 hours, and even this assumes near-adult body weight 4

Additional Safety Considerations

Verify this patient is not receiving paracetamol from other sources:

• Check for combination products containing paracetamol (opioid combinations, cold remedies) 1
• Confirm no recent oral paracetamol administration 1
• Low or absent paracetamol levels do not rule out toxicity if ingestion occurred over several days 1

If pain control is inadequate with appropriate weight-based paracetamol:

• Add adjuvant therapies (NSAIDs once renal function confirmed, regional blocks, or low-dose ketamine) rather than exceeding maximum paracetamol doses 1
• Consider multimodal analgesia approach 1

Summary of Correct Dosing

For your 37 kg, 17-year-old patient:

• Single dose: 555 mg IV (15 mg/kg) 1
• Frequency: Every 6-8 hours 1
• Maximum daily: 2,220 mg (60 mg/kg/day) 1, 3
• Do NOT use standard adult 1000 mg dosing 1