List of products in the National Drug Code with proprietary name . Oseltamivir is used to treat symptoms caused by the flu virus (influenza). It helps make the symptoms (such as stuffy nose, cough, sore throat, fever/chills, aches, tiredness) less severe and shortens the recovery time by 1-2 days. This medication may also be used to prevent the flu if you have been exposed to someone who already has the flu (such as a sick household member) or if there is a flu outbreak in the community. Talk to your doctor for more details. This medication works by stopping the flu virus from growing. It is not a substitute for the flu vaccine. (See also Notes section.)