A beta2-agonist is a type of drug known as a bronchodilator; it helps control the symptoms of asthma by relaxing the muscles lining the bronchial tubes, or airways of the lung. Beta2-agonists are available in both short- and long-acting forms. The short-acting beta2-agonists are used to stop asthma attacks, while the long-acting form is used on a daily basis to improve lung function. Long-acting beta2-agonists are often used in combination with inhaled corticosteroids. For example, formoterol and budesonide (Symbicort) and salmeterol and fluticasone (Advair).