What are the guidelines for Tamiflu (oseltamivir) treatment and prophylaxis in adults and children with influenza A and B?

Tamiflu (Oseltamivir) for Adults and Children: Treatment and Prophylaxis Guidelines

Oseltamivir is the preferred antiviral for both treatment and prophylaxis of influenza A and B in adults and children, with treatment most effective when initiated within 48 hours of symptom onset and prophylaxis within 48 hours of exposure. 1

Treatment Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2
• Initiate within 48 hours of symptom onset for maximum benefit 1
• Can be taken with or without food, though taking with food significantly reduces nausea and vomiting 3, 2

Children (1-12 years) - Weight-Based Dosing

Twice daily for 5 days: 1, 3, 2

• ≤15 kg (≤33 lb): 30 mg twice daily (5 mL oral suspension)

• 15-23 kg (>33-51 lb): 45 mg twice daily (7.5 mL oral suspension)

• 23-40 kg (>51-88 lb): 60 mg twice daily (10 mL oral suspension)

• 40 kg (>88 lb): 75 mg twice daily (12.5 mL oral suspension)

Infants (2 weeks to <1 year)

Twice daily for 5 days: 1, 3

• 9-11 months: 3.5 mg/kg per dose
• Term infants 0-8 months: 3.0 mg/kg per dose
• FDA approved for infants as young as 2 weeks 1, 2

Preterm Infants - Postmenstrual Age-Based Dosing

Twice daily for 5 days: 1, 3

• <38 weeks postmenstrual age: 1.0 mg/kg per dose
• 38-40 weeks postmenstrual age: 1.5 mg/kg per dose
• >40 weeks postmenstrual age: 3.0 mg/kg per dose

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 4, 2
• Post-exposure prophylaxis: 10 days (initiate within 48 hours of exposure) 4, 2
• Community outbreak/seasonal prophylaxis: Up to 6 weeks 2

Children (1-12 years) - Weight-Based Dosing

Once daily for 10 days (or up to 6 weeks during community outbreak): 3, 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

Infants (3-11 months)

• 3.0 mg/kg once daily for 10 days 3, 2
• Prophylaxis NOT recommended for infants <3 months unless situation is critical due to limited safety data 3, 4

Renal Impairment Dose Adjustments

Creatinine Clearance 10-30 mL/min

Treatment: 1, 3, 2

• 75 mg once daily (instead of twice daily) for 5 days

Prophylaxis: 1, 3, 2

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

End-Stage Renal Disease (ESRD)

On hemodialysis: 2

• Treatment: 30 mg immediately, then 30 mg after every hemodialysis cycle (not to exceed 5 days)
• Prophylaxis: 30 mg immediately, then 30 mg after alternate hemodialysis cycles

On CAPD: 2

• Treatment: Single 30 mg dose immediately
• Prophylaxis: 30 mg immediately, then 30 mg once weekly

Not recommended for ESRD patients not undergoing dialysis 2

Who Should Receive Treatment

Mandatory Treatment (Regardless of Vaccination Status)

1

• All hospitalized children with suspected or confirmed influenza
• Children with severe, complicated, or progressive illness attributable to influenza
• Children at high risk of complications (chronic cardiac/pulmonary disease, immunosuppression, diabetes, renal disease, neurodevelopmental disorders, age <2 years)

Consider Treatment For

1

• Any otherwise healthy child with suspected influenza (greatest benefit within 48 hours, but consider even if >48 hours with progressive illness)
• Children whose siblings or household contacts are <6 months or have high-risk conditions

Who Should Receive Prophylaxis

Post-Exposure Prophylaxis Indications

4, 5

• Household or close contacts of confirmed/suspected influenza cases
• High-risk children who have not yet received vaccination or within 2 weeks after vaccination
• Unimmunized family members/healthcare workers with close contact to high-risk children or infants <6 months
• Control of institutional outbreaks in unimmunized staff and children

Important Prophylaxis Considerations

4

• Prophylaxis is NOT a substitute for annual vaccination
• Protection lasts only while medication is continued
• Alternative strategy: Provide prescription for immediate treatment if symptoms develop (75 mg twice daily for 5 days) rather than prophylaxis

Clinical Efficacy

Treatment Benefits

1, 6

• Reduces symptom duration by 26-36 hours (approximately 1-1.5 days)
• Reduces risk of otitis media by 34% in children
• Reduces hospitalization and death risk when initiated early
• Reduces severity of illness by up to 38%

Prophylaxis Efficacy

4, 6, 7

• 70-89% reduction in laboratory-confirmed influenza with post-exposure prophylaxis
• 82-84% efficacy in preventing febrile influenza during seasonal prophylaxis
• Household prophylaxis: NNTB = 7 (highly effective)

Common Adverse Effects and Management

Most Common Side Effects

1, 3, 2, 7

• Nausea: 10% of adults (vs 6% placebo)
• Vomiting: 9% of adults (vs 3% placebo); 14.3% of children (vs 8.5% placebo)
• Headache
• Only ~1% discontinue due to gastrointestinal effects

Key Management Strategy

3, 2

• Taking oseltamivir with food significantly reduces nausea and vomiting severity
• Gastrointestinal effects are mild, transient, and manageable

Neuropsychiatric Events

1, 2

• No established causal link between oseltamivir and neuropsychiatric events
• Influenza itself increases risk of confusion/abnormal behavior, particularly in children
• Monitor for signs of abnormal behavior during illness

Formulation and Administration

Available Forms

1, 3, 2

• Capsules: 30 mg, 45 mg, 75 mg
• Oral suspension: 6 mg/mL (when reconstituted from powder)

Administration Tips

3, 2

• Capsules can be opened and contents mixed with liquid if patient cannot swallow whole
• If commercial suspension unavailable, pharmacies can compound suspension from capsules
• Preferred concentration: 6 mg/mL

Critical Pitfalls to Avoid

Do NOT Delay Treatment

1

• Do not wait for laboratory confirmation in high-risk patients or during influenza season
• Clinical judgment based on symptoms and local influenza activity is sufficient
• Treatment after 48 hours still provides benefit in moderate-to-severe or progressive disease

Drug Interaction Warning

3, 2

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use
• Do not use oseltamivir for 14 days after LAIV vaccination unless medically indicated

Resistance Considerations

4, 2

• If patient develops influenza symptoms while on prophylaxis, may indicate oseltamivir-resistant strain
• Requires immediate medical evaluation

Renal Function Monitoring

3, 8

• Always assess renal function in elderly patients (≥65 years) before dosing
• Dose reduction mandatory when creatinine clearance <60 mL/min
• Age alone does not require dose adjustment—renal function is the key determinant