What is the recommended treatment for a patient diagnosed with influenza, considering treatment with Tamiflu (oseltamivir)?

Tamiflu (Oseltamivir) Treatment for Influenza

For adults and adolescents ≥13 years with influenza, treat with oseltamivir 75 mg twice daily for 5 days, ideally within 48 hours of symptom onset, though high-risk and hospitalized patients benefit even when treatment starts beyond 48 hours. 1, 2

Treatment Dosing by Age and Weight

Adults and Adolescents (≥13 years)

• 75 mg twice daily for 5 days 1, 2
• Administer with or without food, though taking with meals may reduce gastrointestinal side effects 1, 2
• Adjust dose for renal impairment: if creatinine clearance 10-30 mL/min, reduce to 75 mg once daily for 5 days 1

Pediatric Patients (Weight-Based Dosing)

Children ≥12 months: 1, 2

• ≤15 kg (≤33 lb): 30 mg twice daily

• 15-23 kg (>33-51 lb): 45 mg twice daily

• 23-40 kg (>51-88 lb): 60 mg twice daily

• 40 kg (>88 lb): 75 mg twice daily

Infants 9-11 months: 3.5 mg/kg per dose twice daily 1, 2

Term infants 0-8 months: 3 mg/kg per dose twice daily 1, 2

Preterm infants (by postmenstrual age): 1

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

• 40 weeks: 3.0 mg/kg per dose twice daily

Timing of Treatment Initiation

Optimal window: Within 48 hours of symptom onset 2, 3

• Maximum benefit occurs when started within 24 hours, reducing illness duration by approximately 1-1.5 days in healthy adults 4, 3, 5
• Starting within 12 hours reduces illness duration by 3.1 days compared to starting at 48 hours 5

Critical exception—DO NOT withhold treatment beyond 48 hours in: 4

• All hospitalized patients with suspected influenza
• Severely ill or progressively worsening patients
• Immunocompromised patients (including those on long-term corticosteroids)
• Children <2 years of age (especially infants <6 months)
• Adults ≥65 years
• Pregnant women
• Patients with chronic cardiac or respiratory disease

Evidence for late treatment: Treatment initiated up to 96 hours after symptom onset provides significant mortality benefit in high-risk patients (OR = 0.21 for death within 15 days) 4

Who Should Receive Treatment

Immediate Treatment Required (Do Not Wait for Lab Confirmation)

Hospitalized patients: All patients hospitalized with suspected influenza, regardless of symptom duration or vaccination status 4

High-risk outpatients: 4

• Children <2 years (highest hospitalization rates in infants <6 months) 6
• Adults ≥65 years
• Pregnant women
• Immunocompromised patients (HIV, chemotherapy, transplant recipients, chronic corticosteroid use)
• Chronic medical conditions: cardiac disease, pulmonary disease (including asthma), diabetes, renal disease, neurologic disorders

Severely ill patients: Progressive disease, respiratory distress, hypoxia, altered mental status, or signs of sepsis 4

Consider Treatment in Otherwise Healthy Patients

• Symptomatic outpatients presenting within 48 hours during influenza season, especially those living with high-risk household contacts 4
• Greatest benefit when initiated within 24 hours of symptom onset 5

Clinical Benefits Expected

In otherwise healthy patients: 4, 3, 7

• Reduces illness duration by 17.6-29.9 hours (approximately 1-1.5 days)
• Reduces symptom severity by up to 38%
• Faster return to normal activities

In high-risk and hospitalized patients: 4

• 50% reduction in pneumonia risk
• 34% reduction in otitis media in children
• Significant mortality benefit (OR = 0.21 for death within 15 days)
• Reduced hospitalization rates in outpatients
• Decreased antibiotic use and secondary complications 7

Prophylaxis Dosing

Post-Exposure Prophylaxis

Initiate within 48 hours of exposure to infected individual 2

Adults and adolescents ≥13 years: 75 mg once daily for 10 days 1, 2

Children 1-12 years (weight-based): 1, 2

• ≤15 kg: 30 mg once daily

• 15-23 kg: 45 mg once daily

• 23-40 kg: 60 mg once daily

• 40 kg: 75 mg once daily

Duration: 10 days for household contacts; up to 6 weeks during community outbreaks 2

Immunocompromised patients: May continue prophylaxis up to 12 weeks 2

Indications for Prophylaxis

• Household contacts of influenza-infected persons, especially high-risk individuals 4
• Institutional outbreak control in nursing homes—all eligible residents regardless of vaccination status, continued ≥2 weeks or until 1 week after outbreak ends 4
• Unvaccinated healthcare workers in outbreak settings caring for high-risk patients 4

Common Pitfalls to Avoid

Do not wait for laboratory confirmation in high-risk patients 4

• Rapid antigen tests have poor sensitivity; negative results should not exclude treatment
• Start empirically based on clinical presentation during influenza season
• RT-PCR is gold standard but takes longer—do not delay treatment awaiting results

Do not withhold treatment based on time since symptom onset in high-risk populations 4

• Multiple studies demonstrate mortality benefit when treatment initiated up to 96 hours after onset in hospitalized patients
• The 48-hour window applies primarily to otherwise healthy outpatients for symptomatic benefit

Do not reflexively add antibiotics for viral influenza symptoms alone 4

• Only add antibiotics if bacterial superinfection is suspected (new consolidation on imaging, purulent sputum, clinical deterioration despite oseltamivir, elevated inflammatory markers)
• Common bacterial superinfections: S. pneumoniae, S. aureus, H. influenzae

Adverse Effects

Most common: 4, 3, 7

• Nausea (3.66% increased risk; NNTH = 28)
• Vomiting (4.56% increased risk; NNTH = 22; more prominent in children at 5.34% increased risk, NNTH = 19)
• Diarrhea (may occur in infants <1 year)

Important characteristics: 4, 7

• Gastrointestinal effects are transient and mild
• Rarely lead to discontinuation (overall discontinuation rate 1.8%)
• Taking with food significantly improves tolerability
• No established link between oseltamivir and neuropsychiatric events, though monitoring recommended

Special Populations

Renal impairment: 1

• CrCl 10-30 mL/min: 75 mg once daily for 5 days (treatment) or 30 mg once daily for 10 days (prophylaxis)
• Not recommended for end-stage renal disease patients not undergoing dialysis 2

Pregnant women: Treatment recommended; benefits outweigh risks during pregnancy 4

Patients with hereditary fructose intolerance: Oseltamivir oral suspension contains sorbitol, which may cause dyspepsia and diarrhea 4

Important Limitations

Oseltamivir is NOT a substitute for annual influenza vaccination 2

• Vaccination remains the primary prevention strategy
• Oseltamivir is an adjunct, not a replacement for vaccination 1

Resistance considerations: 4

• Oseltamivir resistance in influenza A remains <5% in the United States
• If resistance suspected, zanamivir is an alternative
• Oseltamivir appears less effective against influenza B compared to influenza A