Drug of the Day: Oseltamivir. Oseltamivir is a key antiviral used to treat and prevent influenza. It works by blocking neuraminidase, an enzyme the virus uses to escape infected cells and spread through the respiratory tract. By stopping this process, the virus is contained and its spread is limited. The most important rule: timing matters. Oseltamivir works best when started early—ideally within 48 hours of symptoms—when the virus is actively replicating. It’s commonly used during flu season, e