What prescription medications are recommended for treating influenza (flu)?

Prescription Medications for Influenza

For otherwise healthy outpatients with influenza, oseltamivir 75 mg twice daily for 5 days is the preferred prescription treatment when initiated within 48 hours of symptom onset, though the benefit is modest (reducing illness duration by approximately 1 day) and treatment is optional rather than mandatory. 1

Treatment Recommendations by Patient Risk Status

Low-Risk Patients (Otherwise Healthy)

• Treatment is optional and can be considered based on patient preference for a modest reduction in illness duration of approximately 0.7-1.5 days when started within 48 hours of symptom onset 1
• The Infectious Diseases Society of America and American College of Physicians recommend oral oseltamivir 75 mg twice daily for 5 days as the preferred option if treatment is chosen 1
• Alternative: inhaled zanamivir 10 mg (two 5-mg inhalations) twice daily for 5 days for patients who prefer inhalation or cannot tolerate oseltamivir 1
• Important caveat: The quality of evidence for clinically important outcomes like hospitalization and mortality is very low to low quality in this population 1
• Treatment ideally should be started within 24 hours of symptom onset for maximum benefit 1

High-Risk Patients (Severe or Complicated Influenza)

• Oseltamivir is conditionally recommended for severe influenza 2
• Treatment should be initiated even if more than 48 hours have passed since symptom onset in hospitalized or severely ill patients 3
• Immunocompromised patients may require longer treatment courses than the standard 5 days 4

Available Prescription Antiviral Medications

Oseltamivir (Tamiflu)

Adults:

• Treatment: 75 mg orally twice daily for 5 days 3, 4
• Prophylaxis: 75 mg orally once daily for 10 days (post-exposure) or up to 6 weeks (seasonal) 3

Pediatric Dosing (≥12 months, weight-based):

• ≤15 kg: 30 mg twice daily 3

• 15-23 kg: 45 mg twice daily 3

• 23-40 kg: 60 mg twice daily 3

• 40 kg: 75 mg twice daily 3

Infants (birth to <12 months):

• 9-11 months: 3.5 mg/kg per dose twice daily 3
• 0-8 months (term): 3 mg/kg per dose twice daily 3
• Preterm infants: dosing varies by postmenstrual age (1.0-3.0 mg/kg per dose twice daily) 3

Key considerations:

• FDA-approved for treatment in patients ≥2 weeks of age 4
• Can be taken with or without food, though food may improve gastrointestinal tolerability 3, 4
• Requires dose adjustment in renal insufficiency (creatinine clearance 10-30 mL/min: 75 mg once daily for treatment) 3

Zanamivir (Relenza)

Adults and Children:

• Treatment: 10 mg (two 5-mg inhalations) twice daily for 5 days 3, 5
• Prophylaxis: 10 mg (two 5-mg inhalations) once daily for 10 days 3

Key considerations:

• FDA-approved for treatment in patients ≥7 years and prophylaxis in patients ≥5 years 3, 5
• Not recommended for patients with underlying airways disease (asthma or COPD) due to risk of bronchospasm 5
• Administered via DISKHALER inhalation device 5
• If using inhaled bronchodilator, use it before zanamivir 5

Peramivir

Adults:

• One 600-mg intravenous infusion over 15-30 minutes (single dose) 3

Pediatric:

• Ages 2-12 years: 12 mg/kg (maximum 600 mg) IV over 15-30 minutes 3
• Ages 13-17 years: 600 mg IV over 15-30 minutes 3

Key considerations:

• Not recommended for prophylaxis 3
• Single-dose IV treatment option 3

Baloxavir (Xofluza)

Patients ≥12 years and >40 kg:

• 40-80 kg: 40 mg orally (single dose) 3, 6
• ≥80 kg: 80 mg orally (single dose) 3, 6

Key considerations:

• Single-dose oral treatment 3, 6
• Same dosing for treatment and prophylaxis 6
• FDA-approved for prophylaxis 6
• Conditionally recommended for non-severe influenza if risk of severe illness is high 2

Critical Timing Considerations

• Treatment is most effective when initiated within 24 hours of symptom onset 1
• Treatment within 48 hours provides some benefit 3, 1
• For severely ill or hospitalized patients, treatment may be beneficial even beyond 48 hours 3
• Post-exposure prophylaxis should be initiated within 48 hours of contact with infected individual 4

Important Clinical Pitfalls

Antibiotic Use

• Antibiotics are NOT routinely recommended for previously well adults with acute bronchitis complicating influenza in the absence of pneumonia 3
• Consider antibiotics only if patients develop worsening symptoms (recrudescent fever or increasing dyspnea) 3
• Oseltamivir treatment may reduce antibiotic prescriptions (20% vs 38% in untreated patients) 1

Bacterial Co-infection

• Investigate and empirically treat bacterial co-infection if patients deteriorate after initial improvement or fail to improve after 3-5 days of antiviral treatment 1
• For severe influenza-related pneumonia, use combination parenteral antibiotics (broad-spectrum β-lactamase stable antibiotic plus macrolide) 3

Drug Interactions

• Avoid administration of live attenuated influenza vaccine (LAIV) within 2 weeks before or 48 hours after oseltamivir administration 4

Special Populations

• Renal impairment: Adjust oseltamivir dose based on creatinine clearance 3, 4
• Hereditary fructose intolerance: One 75 mg dose of oseltamivir oral suspension contains 2 grams of sorbitol, which exceeds daily maximum and may cause dyspepsia and diarrhea 4
• Pregnancy: Available information indicates oseltamivir does not increase risk of birth defects 4
• Immunocompromised: May continue prophylaxis for up to 12 weeks 4

Serious Adverse Effects to Monitor

• Bronchospasm with zanamivir: Serious breathing problems including death have occurred; stop immediately if wheezing, shortness of breath, or chest tightness develops 5
• Neuropsychiatric events: Patients with influenza may develop confusion, speech problems, seizures, or hallucinations; contact physician immediately if these occur 4
• Serious allergic reactions: Stop medication and seek emergency care for skin rash, blisters, facial swelling, or difficulty breathing 4, 5, 4

Vaccination Reminder

• Antiviral medications do not replace annual influenza vaccination 4
• Patients should continue receiving annual flu vaccination according to immunization guidelines 4