Medications for Influenza Treatment
Neuraminidase inhibitors—specifically oseltamivir, zanamivir, peramivir, and baloxavir—are the medications used to treat influenza virus, with oseltamivir being the first-line agent for most patients. 1, 2
Primary Treatment Options
Oseltamivir (First-Line Agent)
Oseltamivir is the antiviral drug of choice for influenza management because it is orally administered, effective against both influenza A and B, and has the broadest approval across age groups. 1, 2
Dosing for adults: 75 mg orally twice daily for 5 days 3, 1, 4
Pediatric dosing (weight-based): 3, 1
- ≤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
Renal adjustment required: Reduce dose by 50% (to 75 mg once daily) if creatinine clearance <30 mL/min 3, 1
Zanamivir (Alternative Agent)
Zanamivir is administered via oral inhalation at 10 mg (2 inhalations) twice daily for 5 days. 1, 5 This agent is contraindicated in patients with underlying airway disease (asthma, COPD, reactive airways) due to risk of severe bronchospasm. 1, 6, 5
Peramivir (IV Formulation)
Peramivir is an intravenous neuraminidase inhibitor reserved for patients who cannot absorb oral oseltamivir or tolerate inhaled zanamivir, approved for patients ≥2 years who have been symptomatic ≤2 days. 1
Baloxavir (Newer Agent)
Baloxavir is a cap-dependent endonuclease inhibitor with activity against influenza A and B, conditionally recommended for non-severe influenza in high-risk patients. 1
Medications NOT Recommended
Adamantanes (amantadine and rimantadine) are NOT recommended for current influenza treatment due to widespread resistance among circulating strains. 3, 1, 4 These agents are only active against influenza A (not B), and current H3N2 and H1N1 strains show high resistance rates. 1, 4
Critical Timing Principles
Maximum benefit occurs when treatment is initiated within 48 hours of symptom onset, with treatment within 12 hours providing the greatest reduction in illness duration. 1, 7 Oseltamivir reduces illness duration by approximately 24 hours when started early. 3, 1, 2, 8
For hospitalized patients, initiate treatment immediately regardless of time since symptom onset. 1, 4 Do not delay treatment while waiting for laboratory confirmation in high-risk patients during influenza season. 1, 6
High-Risk Populations Requiring Immediate Treatment
High-risk patients who should receive immediate antiviral treatment include: 1, 4
- Children <2 years and adults ≥65 years
- Pregnant and postpartum women
- Patients with chronic pulmonary disease, cardiovascular disease, or immunocompromising conditions
Common Clinical Pitfalls
Do not use zanamivir in patients with reactive airway disease or active wheezing—this is an absolute contraindication. 1, 6, 5 For these patients, oseltamivir is the only appropriate neuraminidase inhibitor. 6
Do not delay treatment waiting for laboratory confirmation in high-risk patients during influenza season, as clinical diagnosis is sufficient to initiate therapy and delays reduce treatment efficacy. 1, 6
Take oseltamivir with food to reduce gastrointestinal side effects (nausea and vomiting), which are the most common adverse events occurring in approximately 10% of patients. 1, 7
Important Limitations
These antiviral medications do not "cure" influenza in the sense of eradicating the virus immediately—they reduce viral replication, thereby shortening illness duration and potentially reducing complications. 3, 8 There is insufficient evidence that antivirals reduce overall mortality. 3 The major clinical benefits are reducing illness duration by approximately 24 hours, decreasing hospitalizations, and reducing secondary antibiotic use. 3, 8