beta-adrenergic agonist beta-adrenergic agonist beta adrenergic agonists or beta agonists are medications that relax muscles of the airways, causing widening of the airways and resulting in easier breathing. they are a class of sympathomimetic agents, each acting upon the beta adrenoceptors. in general, pure beta-adrenergic agonists have the opposite function of beta blockers: beta-adrenoreceptor agonist ligands mimic the actions of both epinephrine- and norepinephrine- signaling, in the heart and lungs, and in smooth muscle tissue; epinephrine expresses the higher affinity. the activation of β1, β2 and β3 activates the enzyme, adenylate cyclase. this, in turn, leads to the activation of the secondary messenger cyclic adenosine monophosphate (camp); camp then activates protein kinase a (pka) which phosphorylates target proteins, ultimately inducing smooth muscle relaxation and contraction of the cardiac tissue. beta adrenergic receptor agonistsdrug classskeletal structure formula of salbutamol (albuterol) — a widely used medication to treat asthma attacksclass identifiersusebradycardia, asthma, heart failure, etc.atc coder03biological targetadrenergic receptors (β subtype)