What is the recommended dosage of medications for treating viral fever?

Drug Dosage in Viral Fever

For symptomatic treatment of viral fever, use acetaminophen (paracetamol) as first-line therapy at standard doses: 500-1000 mg every 4-6 hours for adults (maximum 4 doses/24 hours), and 15 mg/kg per dose every 4-6 hours for children (maximum 4 doses/24 hours). 1, 2

Antipyretic Therapy for Viral Fever

Adults and Adolescents ≥13 Years

• Acetaminophen (Paracetamol): 500-1000 mg orally every 4-6 hours, maximum 4 doses in 24 hours 1, 2
• Ibuprofen: 400-600 mg orally every 6-8 hours if acetaminophen is insufficient, though acetaminophen should be tried first 3, 4
• Combination therapy: Paracetamol 500 mg/Ibuprofen 150 mg may provide faster fever reduction in the first hour compared to paracetamol alone, particularly for bacterial co-infections 4

Pediatric Patients

Weight-based dosing is preferred for all pediatric patients: 1, 3

• Acetaminophen: 15 mg/kg per dose orally every 4-6 hours (maximum 4 doses/24 hours) 1, 3
• Ibuprofen (for children ≥6 months): 10 mg/kg per dose orally every 6-8 hours (maximum 3 doses/24 hours) 3

Important caveat: Ibuprofen should be considered first-line for fever in children ≥6 months, as it may provide an additional 2.5 hours without fever over 24 hours compared to paracetamol alone 3

Critical Safety Warnings

• Never use aspirin in children ≤18 years with suspected viral illness due to risk of Reye's syndrome 1
• Avoid over-the-counter cold medications in children <4 years without consulting a healthcare provider first 1
• Carefully record all dose times when using combination therapy to avoid exceeding maximum recommended doses (occurred in 8% for paracetamol and 11% for ibuprofen in one study) 3

Antiviral Therapy (When Influenza is Confirmed or Suspected)

Oseltamivir Dosing for Influenza A and B

Initiate treatment within 48 hours of symptom onset for maximum benefit, though later treatment may still provide benefit in moderate-to-severe disease. 1, 5, 6

Adults and Adolescents ≥13 Years

• Treatment: 75 mg orally twice daily for 5 days 1, 5, 7, 6
• Prophylaxis: 75 mg orally once daily for 10 days (post-exposure) or up to 6 weeks (community outbreak) 1, 5, 7, 6

Pediatric Patients ≥12 Months (Weight-Based)

Treatment dosing (twice daily for 5 days): 1, 5, 6

• ≤15 kg: 30 mg twice daily

• 15-23 kg: 45 mg twice daily

• 23-40 kg: 60 mg twice daily

• 40 kg: 75 mg twice daily

Prophylaxis dosing (once daily for 10 days): Same weight-based doses as treatment, but administered once daily instead of twice daily 1, 5

Infants <12 Months

• 9-11 months: 3.5 mg/kg per dose twice daily for treatment; 3.5 mg/kg once daily for prophylaxis 1, 5
• 0-8 months (term infants): 3 mg/kg per dose twice daily for treatment; 3 mg/kg once daily for prophylaxis (ages 3-8 months only) 1, 5, 6
• Prophylaxis not recommended for infants <3 months unless situation is critical, due to limited safety data 1, 5

Preterm Infants

Dosing based on postmenstrual age (twice daily for 5 days): 5, 7

• <38 weeks: 1.0 mg/kg twice daily
• 38-40 weeks: 1.5 mg/kg twice daily

• 40 weeks: 3.0 mg/kg twice daily

Critical note: Standard term infant dosing may lead to very high drug concentrations in preterm infants due to immature renal function 1

Renal Impairment Adjustments

For creatinine clearance 10-30 mL/min: 1, 5, 6

• Treatment: 75 mg once daily for 5 days
• Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses)

Oseltamivir is not recommended for end-stage renal disease patients not undergoing dialysis 6

Formulation and Administration

• Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules) 1, 5, 6
• Capsules: 30 mg, 45 mg, 75 mg 1, 6
• May be taken with or without food, though administration with food may improve gastrointestinal tolerability 1, 7, 6

Key Clinical Considerations

Fever Response Does Not Predict Etiology

The fever response to acetaminophen cannot distinguish between viral and bacterial infections - both show similar temperature reductions after antipyretic administration 8. Therefore, clinical judgment and appropriate diagnostic testing remain essential for determining infection etiology.

Timing of Antiviral Therapy

Treatment initiated within 48 hours provides optimal benefit, but treatment after 48 hours in patients with moderate-to-severe or progressive disease has shown benefit and should be strongly considered 1

Common Pitfalls to Avoid

• Do not withhold oseltamivir based on negative rapid antigen tests if clinical suspicion is high, as these tests have limited sensitivity 1
• Do not delay antiviral treatment while awaiting confirmatory testing in high-risk patients or those with severe illness 1
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 5