What is the correct dosing regimen for combining paracetamol (acetaminophen) and ibuprofen for a 7-year-old child weighing 20kg?

Combining Paracetamol and Ibuprofen for a 7-Year-Old Child (20kg)

For a 20kg child, give paracetamol 300mg (15 mg/kg) every 4-6 hours and ibuprofen 200mg (10 mg/kg) every 6-8 hours, staggering the doses so medications are given every 3-4 hours when both are needed. 1

Specific Dosing Calculations

Paracetamol dosing:

• Dose: 300mg per dose (15 mg/kg × 20kg) 1
• Frequency: Every 4-6 hours 1
• Maximum: 1200mg per day (60 mg/kg/day) or 4 doses in 24 hours 1

Ibuprofen dosing:

• Dose: 200mg per dose (10 mg/kg × 20kg) 1
• Frequency: Every 6-8 hours 1
• Maximum: 3 doses in 24 hours 1

How to Alternate the Medications

When using both medications together, stagger them so the child receives medication every 3-4 hours rather than simultaneously. 1 For example:

• Time 0:00 - Give paracetamol 300mg
• Time 3:00 - Give ibuprofen 200mg
• Time 6:00 - Give paracetamol 300mg
• Time 9:00 - Give ibuprofen 200mg
• Continue this pattern as needed

This alternating approach provides an additional 2.5 hours without fever over 24 hours compared to ibuprofen alone 2 and 4.4 hours more fever-free time compared to paracetamol alone. 2

Evidence Supporting Combination Therapy

The combination approach is supported by high-quality evidence showing superior efficacy:

• The PITCH trial (2009) demonstrated that combined therapy provided significantly more time without fever in the first 24 hours compared to either medication alone 2
• A 2023 prospective study confirmed that the combination showed enhanced effectiveness in fever and pain relief with minimal adverse effects 3
• The combination clears fever faster than paracetamol alone (23 minutes faster) and provides comparable speed to ibuprofen monotherapy 2

Critical Safety Considerations

The most important safety concern is accidentally exceeding the maximum recommended dose when using both medications. 2 To prevent this:

• Record all dose times carefully - write down every administration 2
• Never give more than 4 doses of paracetamol in 24 hours 1
• Never give more than 3 doses of ibuprofen in 24 hours 1
• In the PITCH trial, 8% of children exceeded the maximum paracetamol doses and 11% exceeded ibuprofen doses when using combination therapy 2

Paracetamol toxicity risk: Single exposures greater than 140 mg/kg/day for several days carry serious toxicity risk 4. For a 20kg child, this would be 2800mg/day - well above the recommended 1200mg/day maximum.

When to Use Combination vs. Monotherapy

Start with ibuprofen monotherapy first for most febrile children. 2 The relative benefits of adding paracetamol (extra 2.5 hours without fever over 24 hours) must be weighed against the risk of inadvertently exceeding maximum doses. 2

Consider combination therapy when:

• Fever-associated discomfort is significant (higher discomfort correlates with higher temperatures) 2
• Single-agent therapy provides inadequate symptom control
• Parents can reliably track and record all medication doses 2

Cost and Practical Considerations

Combination therapy is actually the most cost-effective option due to lower use of healthcare services: £14 for combination vs. £20 for paracetamol alone vs. £18 for ibuprofen alone in the PITCH trial. 2 Parents also saved money through reduced travel costs and less time off work. 2

Expected Clinical Course

Parents should understand that fever is relatively short-lived: only one-quarter of children were "back to normal" by 48 hours and one-third by day 5 in the PITCH trial. 2 This helps set realistic expectations regardless of which medication regimen is used.