List of products in the National Drug Code with proprietary name . Flunisolide is used to prevent and control symptoms (wheezing and shortness of breath) caused by asthma. This medication belongs to a class of drugs known as corticosteroids. It works directly in the lungs to make breathing easier by reducing the irritation and swelling of the airways. This medication must be used regularly to prevent breathing problems (attacks of wheezing/shortness of breath). It does not work right away and should not be used to relieve an asthma attack. If an attack occurs, use your quick-relief inhaler as prescribed.