Paracetamol Dosing for a 12-Year-Old, 20 kg Patient
For a 12-year-old child weighing 20 kg, administer paracetamol 10-15 mg/kg per dose (200-300 mg) every 4-6 hours, not exceeding 5 doses in 24 hours or a maximum daily dose of 60-75 mg/kg (1200-1500 mg/day). 1, 2, 3
Weight-Based Dosing Algorithm
This patient requires weight-based dosing rather than age-based dosing due to significant underweight status for age:
- Single dose: 10-15 mg/kg = 200-300 mg per dose 1, 3
- Dosing interval: Every 4-6 hours 1, 2
- Maximum frequency: Not to exceed 5 doses in 24 hours 1
- Maximum daily dose: 60-75 mg/kg/day = 1200-1500 mg/day 2, 3
Critical Dosing Considerations
This child is significantly underweight for age (typical 12-year-old weighs 35-45 kg), making age-based dosing dangerous:
- The FDA label recommends 650 mg per dose for children ≥12 years 1, which would be 32.5 mg/kg for this 20 kg child—more than double the safe maximum single dose 1, 3
- Age-based guidelines place underweight children at high risk of exceeding therapeutic limits and approaching toxic doses 4
- Always use weight-based dosing for children outside typical weight ranges 3, 4
Practical Administration
Recommended approach for this patient:
- Start with 10 mg/kg (200 mg) per dose every 4-6 hours 3
- May increase to 15 mg/kg (300 mg) per dose if inadequate fever/pain control and no adverse effects 2, 3
- Use oral suspension (typically 160 mg/5 mL concentration): give 6.25-9.4 mL per dose 1
- Ensure caregivers carefully record all dose times to prevent accidental overdosing 5
Safety Thresholds and Toxicity Risk
Critical safety limits:
- Therapeutic maximum: 90-95 mg/kg/day 6
- Potential toxicity threshold: >140 mg/kg/day for several days carries serious toxicity risk 2
- Acute overdose concern: Single ingestions >150 mg/kg (>3000 mg for this child) are potentially hepatotoxic 2
For this 20 kg child, even 5 doses of 300 mg = 1500 mg/day = 75 mg/kg/day, which remains well below the toxicity threshold 2, 6
Common Pitfalls to Avoid
- Never use age-based dosing for underweight children—this is the most common prescribing error leading to overdose 4
- Do not exceed 90 mg/kg/day even if fever persists, as cumulative toxicity can cause hepatic and renal damage 6
- Avoid combination products without verifying the paracetamol component doesn't exceed daily limits 7
- Ensure 4-hour minimum intervals between doses to prevent inadvertent overdosing 1, 2
Monitoring and Follow-Up
- If fever/pain persists beyond 48 hours or worsens, medical re-evaluation is necessary 5
- Consider ibuprofen as first-line alternative (10 mg/kg every 6-8 hours) if paracetamol provides inadequate relief 5
- Combination therapy with ibuprofen may provide additional 2.5-4.4 hours without fever but increases risk of dosing errors 5