Seretide Accuhaler 50mcg/500mcg contains Salmeterol 50mcg and Fluticasone propionate 500mcg which is used in the treatment of asthma and chronic obstructive pulmonary disease. Salmeterol is a long-acting bronchodilator which works by relaxing the muscles in the airways and widens the airways. Fluticasone propionate is a steroid. It works by stopping the release of certain chemical messengers that cause inflammation (swelling) of the airways. Together they make breathing easier.