List of products in the National Drug Code with proprietary name . Zafirlukast is used to control and prevent symptoms (such as wheezing and shortness of breath) caused by asthma. Controlling symptoms of asthma helps you maintain your normal activities and cuts down on time lost from work or school. This medication must be used regularly to be effective. It does not work right away and should not be used to relieve sudden asthma attacks. If an asthma attack occurs, use your quick-relief inhaler (such as albuterol, salbutamol) as prescribed.