The beta-2 adrenergic receptor (β 2 adrenoreceptor), also known as ADRB2, is a cell membrane-spanning beta-adrenergic receptor that interacts with epinephrine, a hormone and neurotransmitter (ligand synonym, adrenaline) whose signaling, via adenylate cyclase stimulation through trimeric Gs proteins, increased cAMP, and downstream L-type . 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.. Beta 2 agonists are a type of bronchodilator used in the treatment of asthma. Beta 2 agonist medications stimulate beta cells, which relax the smooth muscles of your airways that tighten as part of the pathophysiology of asthma to cause symptoms such as:. Beta 2 Agonist Drugs (Selective Beta 2 agonists) are the safest drugs and most effective short acting beta 2 agonist for the treatment of asthma while some long acting beta 2 agonist are added to an inhaled corticosteriod.. General Pharmacology . Beta-adrenoceptor agonists (β-agonists) bind to β-receptors on cardiac and smooth muscle tissues. They also have important actions in other tissues, especially bronchial smooth muscle (relaxation), the liver (stimulate glycogenolysis) and kidneys (stimulate renin release).. Introduction The beta-2 adrenergic agonists are a large group of drugs that mimic the actions of naturally occurring catecholamines such as norepinephrine, epinephrine and dopamine..