Which antiviral drug acts by inhibiting viral neuraminidase and is effective against both influenza A and B?

Explanation

## Neuraminidase Inhibitors **Key Point:** Oseltamivir is a selective inhibitor of influenza neuraminidase, an enzyme essential for viral release from infected cells. It is active against both influenza A and B strains. ### Mechanism of Action Neuraminidase cleaves sialic acid receptors on the host cell surface, allowing newly synthesized viral particles to escape. By blocking this enzyme, oseltamivir traps virions on the cell surface and prevents further spread of infection. ### Clinical Use - **Indication:** Treatment and prophylaxis of influenza A and B - **Dosing:** 75 mg orally twice daily for 5 days (treatment) - **Timing:** Most effective when started within 48 hours of symptom onset ### Comparison with Other Antivirals | Drug | Target | Spectrum | Notes | |------|--------|----------|-------| | Oseltamivir | Neuraminidase | Influenza A & B | Oral bioavailability; prodrug | | Zanamivir | Neuraminidase | Influenza A & B | Inhaled; less GI side effects | | Amantadine | M2 protein | Influenza A only | Older agent; resistance common | | Rimantadine | M2 protein | Influenza A only | Similar to amantadine | **High-Yield:** Oseltamivir and zanamivir are the only antivirals effective against both influenza A and B. Amantadine and rimantadine (M2 inhibitors) work only against influenza A. **Clinical Pearl:** Resistance to neuraminidase inhibitors is less common than to M2 inhibitors, making oseltamivir the preferred first-line agent for seasonal influenza.