Which antiviral drug is commonly used for influenza and within how many hours should it be started for maximum benefit?

• A. Oseltamivir; start within 48 hours of symptom onset
• B. Acyclovir; start within 24 hours
• C. Zanamivir; start within 72 hours
• D. Rimantadine; start within 24 hours

Answer: (A)

Early initiation of antiviral therapy is crucial in influenza because the virus replicates rapidly in the first couple of days, and treatment works best when started while viral activity is high. Oseltamivir is the drug most commonly used for treating influenza, given orally, and it provides the greatest benefit when begun within 48 hours of symptom onset. This timing maximizes reduction in symptom duration and the risk of complications, especially in high-risk patients.

Acyclovir targets herpesviruses, not influenza, so it isn’t used for flu. Zanamivir is another influenza antiviral, but the strongest benefit is still tied to starting treatment within about 48 hours rather than within 72 hours. Rimantadine has fallen out of favor due to widespread resistance and isn’t trusted to provide reliable benefit within a 24-hour window.