β 2 (beta 2) adrenergic receptor agonists, also known as adrenergic β 2 receptor agonists, are a class of drugs that act on the β 2 adrenergic receptor. Like other β adrenergic agonists , they cause smooth muscle relaxation. β 2 adrenergic agonists' effects on smooth muscle cause dilation of bronchial passages , vasodilation in muscle and liver , relaxation of uterine muscle, and release . LABAs (long acting Beta 2 agonist), for example salmeterol and formoterol. People with asthma are most likely to be prescribed a LABA. People with asthma are most likely to be prescribed a LABA. LAMAs (long acting muscarinic antagonist), for example tiotropium.. Uses of long-acting ß2 agonists and current safety advice.. Beta-2 agonists and anticholinergics are available in both short-acting and long-acting forms, whereas theophylline is only available in a long-acting form. Beta-2 agonists They're usually inhaled using a small, hand-held inhaler but may also be available as tablets or syrup.. Beta2-agonists (bronchodilators) are a group of drugs prescribed to treat asthma. Short-acting beta-agonists (SABAs) provide quick relief of asthma symptoms. They can also be prescribed to be taken before exercising in order to prevent exercise-induced bronchoconstriction.. Long-acting Beta-agonist Bronchodilators. The long-acting inhaled beta-agonist bronchodilators, salmeterol (Serevent, Advair) and formoterol (Foradil) have been available to treat asthma since the 1990s..