Salmeterol is called a bronchodilator because it widens (dilates) your airways. It works by opening up the air passages in your lungs so that air can flow into your lungs more freely. This helps to ease symptoms such as coughing, wheezing and feeling breathless. It is prescribed to relieve airways-related problems in people who have asthma or chronic obstructive pulmonary disease (COPD). Salmeterol is called a long-acting bronchodilator. Its effects are usually felt within 20 minutes and last for around 12 hours.