The rational use of β₂-agonists in the management of asthma: Maintenance, rescue, and emergency

β₂-adrenoceptor agonists (β₂-agonists) are the most effective known bronchodilators. In conjunction with antiinflammatory agents, they play an important role in every step of asthma therapy. Rational choice among the many available agents must be based on pharmacologic principles and clinical data. For maintenance therapy designed to optimize lung function and prevent symptoms, a long-acting inhaled β₂-agonist of low intrinsic efficacy offers advantages that are most closely approximated by salmeterol. For rescue therapy in order to relieve acute symptoms, an inhaled β₂-agonist with a rapid onset of action, intermediate duration, and intermediate efficacy is optimal. These features are present in various formulations of albuterol, terbutaline, pirbuterol, and bitolterol. For emergency treatment of acute asthma that does not respond to standard rescue therapy, administration of rescue β₂-agonists at higher doses and increased frequency generally suffices. The full agonists isoproterenol and epinephrine may be required to avert intubation in some patients, however.