A 52-year-old man with type 2 diabetes mellitus and COPD presents with acute influenza B infection confirmed by RT-PCR. He is allergic to oseltamivir (rash). Which is the preferred alternative antiviral agent?

Explanation

## Alternative Neuraminidase Inhibitor When Oseltamivir Contraindicated **Key Point:** When oseltamivir is contraindicated (allergy, intolerance), zanamivir is the preferred alternative neuraminidase inhibitor for influenza A and B. ### Clinical Context This patient has: - **Oseltamivir allergy** (absolute contraindication) - **Influenza B** (rules out M2 inhibitors) - **COPD** (relative contraindication to inhaled zanamivir, but still preferable to M2 inhibitors) ### Zanamivir as Alternative | Property | Zanamivir | |----------|----------| | **Spectrum** | Influenza A + B ✓ | | **Route** | Inhaled (dry powder) | | **Dosing** | 5 mg (2 inhalations) twice daily × 5 days | | **Mechanism** | Neuraminidase inhibitor (same class as oseltamivir) | | **Resistance** | Lower rates than M2 inhibitors | | **Efficacy** | Similar to oseltamivir for symptom reduction | **High-Yield:** Zanamivir is effective against **both influenza A and B**, making it suitable for this patient with confirmed influenza B. Although inhaled administration carries bronchospasm risk in COPD, it is still preferred over M2 inhibitors which: - Are ineffective against influenza B - Have high resistance rates - Cause CNS toxicity ### Managing Bronchospasm Risk with Zanamivir - Pre-treat with short-acting β~2~-agonist (salbutamol) 15 minutes before zanamivir inhalation - Have rescue inhaler available - Monitor closely for respiratory symptoms - If severe bronchospasm occurs, switch to IV peramivir (if available) **Clinical Pearl:** In patients with COPD and influenza B, zanamivir with bronchodilator pre-treatment is the practical first-line alternative when oseltamivir is contraindicated. ### Why Not Peramivir? Although peramivir is a neuraminidase inhibitor available as IV formulation (useful in hospitalized patients unable to take oral/inhaled drugs), it is **not first-line** for outpatient management and is typically reserved for hospitalized or critically ill patients.