19.2 : 抗喘息薬：β2-アドレナリン受容体作動薬

Bronchodilators play a pivotal role in asthma management. They ease airway constriction by relaxing bronchial muscles.

One class of bronchodilators includes β₂-adrenoceptor agonists. These agents target the β₂-adrenoceptors on bronchial smooth muscle cells. This induces muscle relaxation, facilitating the bronchial passages' dilation and relieving symptoms such as wheezing, shortness of breath, and chest tightness.

These agonists are categorized as short-acting β₂-agonists or SABAs and long-acting β₂-agonists or LABAs. SABAs, such as albuterol and terbutaline, provide immediate relief by promptly relaxing airway muscles during acute episodes.

Conversely, LABAs, such as salmeterol and formoterol, sustain bronchodilation and serve as preventive measures for chronic bronchial conditions.

These medications are often administered via metered-dose inhalers or nebulizers to ensure direct and rapid delivery to the respiratory tract.

Despite their benefits, β₂-agonists may yield undesired systemic effects. The most common adverse effect is tremor, while potential side effects encompass tachycardia and cardiac dysrhythmia.