What is the recommended dosage of acetaminophen (paracetamol) and ibuprofen for treating viral fever?

Drug Dosage in Viral Fever

For viral fever in children, use acetaminophen (paracetamol) 15 mg/kg per dose every 4-6 hours (maximum 4 doses/24 hours) as first-line therapy, with ibuprofen 10 mg/kg per dose every 6-8 hours (maximum 3 doses/24 hours) as an equally effective alternative or for persistent fever. 1, 2

Acetaminophen (Paracetamol) Dosing

Pediatric Dosing:

• Standard dose: 15 mg/kg per dose every 4-6 hours 1, 2
• Maximum: 4 doses in 24 hours 3
• Older studies using ≤10 mg/kg doses show inferior efficacy compared to NSAIDs, but 15 mg/kg demonstrates equivalent effectiveness 1

Adult Dosing:

• 500-1000 mg per dose 4
• The 1000 mg dose provides superior fever reduction compared to 500 mg (mean temperature reduction 1.67-1.71°C vs 1.25-1.32°C) 4

Special Populations:

• Pregnant women: Acetaminophen is recommended for fever treatment and is the preferred antipyretic 3
• Children <4 years: Consult healthcare provider before using over-the-counter cold medications 3

Ibuprofen Dosing

Pediatric Dosing:

• 10 mg/kg per dose every 6-8 hours 5, 2
• Maximum: 3 doses in 24 hours 3
• For persistent fever: 0.2 g per dose every 4-6 hours, not exceeding 4 doses/24 hours 6

Adult Dosing:

• 600 mg per dose for viral fever 7
• 500-1000 mg doses show dose-dependent efficacy similar to acetaminophen 4

Critical Safety Considerations

Aspirin Contraindication:

• Never use aspirin in children ≤18 years with suspected viral illness due to Reye's syndrome risk 3
• This includes aspirin-containing products like bismuth subsalicylate 3

Combination Therapy:

• Alternating acetaminophen and ibuprofen every 4 hours provides additional 2.5-4.4 hours without fever over 24 hours compared to monotherapy 2
• The combination reduces fever 23 minutes faster than acetaminophen alone 2
• Major caveat: 8-11% of parents inadvertently exceed maximum recommended doses when using both medications 2
• Recommendation: Carefully record all dose times to prevent overdosing; consider using tracking charts 2

Comparative Efficacy

Acetaminophen vs Ibuprofen:

• When used at appropriate doses (acetaminophen 15 mg/kg, ibuprofen 10 mg/kg), both show equivalent efficacy 1, 4
• Ibuprofen demonstrates superior antipyretic efficacy specifically for bacterial infections 5
• For viral fever in emergency settings, paracetamol/ibuprofen combination (500/150 mg) shows similar efficacy to paracetamol 1000 mg alone 7

Onset and Duration:

• Acetaminophen's antipyretic effect begins within hours but may take up to 4 hours for maximum effect 8
• Both medications show similar time to lowest temperature 4

Management Algorithm for Persistent Fever

If fever persists after initial acetaminophen dose:

1. Wait 4 hours for maximum effect before adding second agent 8
2. Add ibuprofen if temperature remains >38.5°C (101°F) 8
3. Consider physical cooling methods (tepid sponging) as adjunct 3, 8
4. Ensure adequate fluid intake (up to 2 liters/day in adults) 6, 8

When to escalate care:

• Fever persists despite combined therapy 8
• Signs of clinical deterioration 8
• Altered mental status, severe headache, neck stiffness, or respiratory distress 8

Tolerability Profile

• Acetaminophen shows similar tolerability to placebo when used short-term 1
• For consecutive days of treatment, acetaminophen has lower adverse event risk compared to NSAIDs 1
• No significant difference in adverse effects between treatment groups in controlled trials 2, 4
• Acetaminophen has no significant drug interactions with common antivirals (lopinavir/ritonavir, remdesivir, hydroxychloroquine) 6