Seretide Evohaler 50 mcg is a combination inhaler used to treat asthma and chronic obstructive pulmonary disease (COPD). It contains two active ingredients: Salmeterol: A long-acting beta-agonist (LABA) that helps to relax and open the airways, making it easier to breathe.Fluticasone propionate: A corticosteroid that reduces inflammation in the airways.The 250 mcg refers to the dosage of fluticasone in each inhalation, while the amount of salmeterol is usually fixed. The inhaler is used as a maintenance treatment, not for immediate relief during an asthma or COPD attack.