A 38-year-old woman from Delhi presents to the emergency department with a 3-day history of high fever (39.8°C), severe myalgia, headache, and dry cough. She reports that her 6-year-old son had similar symptoms 5 days ago. On examination, she is febrile and tachypneic (RR 24/min) but oxygen saturation is 96% on room air. Throat swab RT-PCR for influenza A is positive. She has no significant comorbidities and is not pregnant. What is the most appropriate antiviral therapy?

Explanation

## Antiviral Management of Influenza A **Key Point:** Oseltamivir (Tamiflu) is the first-line neuraminidase inhibitor for treatment of confirmed influenza A in non-severe cases, particularly when started within 48 hours of symptom onset. ### Mechanism and Efficacy Neuraminidase inhibitors (oseltamivir, zanamivir) block viral release from infected cells by preventing sialic acid cleavage. Oseltamivir is preferred because: - Oral bioavailability (~80%) - Rapid absorption and tissue distribution - Reduces symptom duration by ~1 day if started early - Reduces risk of complications in at-risk groups ### Why Oseltamivir 75 mg BD for 5 days? This is the standard therapeutic dose. The patient: - Presents within 48 hours of symptom onset (optimal window) - Has no contraindications (not pregnant, normal renal function) - Has uncomplicated influenza (oxygen saturation normal, no pneumonia) - Is not severely immunocompromised **Clinical Pearl:** Neuraminidase inhibitors must be started early (ideally <48 hours) to provide maximum benefit. Starting after 48 hours offers minimal symptomatic relief but may still reduce complications in hospitalized patients. ### Comparison of Antivirals | Agent | Class | Route | Dosing | Notes | |-------|-------|-------|--------|-------| | Oseltamivir | Neuraminidase inhibitor | Oral | 75 mg BD × 5 days | First-line; excellent bioavailability | | Zanamivir | Neuraminidase inhibitor | Inhaled | 5 mg BD × 5 days | Alternative; avoid in COPD/asthma | | Amantadine | M2 channel blocker | Oral | 100 mg OD × 7–10 days | Resistance common; rarely used now | | Rimantadine | M2 channel blocker | Oral | 100 mg BD × 7 days | Similar resistance issues; not preferred | **High-Yield:** M2 channel blockers (amantadine, rimantadine) are now rarely recommended due to widespread resistance in circulating influenza A strains globally. Neuraminidase inhibitors are the standard of care. **Mnemonic:** **NANI** = Neuraminidase inhibitors Are Now Indicated (oseltamivir, zanamivir, peramivir).