A 38-year-old woman from Delhi presents to the emergency department with a 3-day history of sudden-onset fever (39.5°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, tachycardic (HR 110/min), and has clear lung fields. Rapid influenza diagnostic test (RIDT) is positive. Chest X-ray is normal. Which of the following antiviral agents is most appropriate for this patient if started within 48 hours of symptom onset?

Explanation

## Antiviral Management of Influenza **Key Point:** Oseltamivir (a neuraminidase inhibitor) is the first-line antiviral for symptomatic influenza when initiated within 48 hours of symptom onset. It reduces symptom duration by approximately 1 day and decreases risk of complications. ## Clinical Context This patient presents with classic influenza presentation: - Acute onset fever, myalgia, headache, cough - Positive RIDT confirming influenza diagnosis - Within 48-hour treatment window (critical for efficacy) - Normal chest X-ray (uncomplicated influenza) ## Mechanism of Oseltamivir Oseltamivir is a prodrug converted to oseltamivir carboxylate, which inhibits viral neuraminidase—the enzyme responsible for release of progeny virions from infected cells. This prevents viral spread and reduces symptom severity and duration. ## Dosing in Adults **High-Yield:** Oseltamivir 75 mg orally twice daily for 5 days is the standard regimen for treatment of uncomplicated influenza in adults. ## Timing Matters **Clinical Pearl:** Maximum benefit occurs when antiviral therapy is initiated within 48 hours of symptom onset. Starting after 48 hours provides minimal clinical benefit in uncomplicated cases, though may still be considered in hospitalized or severely ill patients. ## Comparison with Other Agents | Agent | Class | Use in Influenza | Limitation | |-------|-------|------------------|------------| | Oseltamivir | Neuraminidase inhibitor | First-line treatment | Must start within 48 hrs | | Zanamivir | Neuraminidase inhibitor | Alternative (inhaled) | Respiratory adverse effects | | Peramivir | Neuraminidase inhibitor | IV option for hospitalized | Limited availability | | Amantadine | M2 channel blocker | Rarely used now | High resistance rates | | Rimantadine | M2 channel blocker | Rarely used now | High resistance rates | **Warning:** M2 inhibitors (amantadine, rimantadine) are no longer recommended due to widespread resistance in circulating influenza strains.