bèta2agonisten

Beta‑2 agonists are medications that selectively stimulate beta‑2 adrenergic receptors located primarily on smooth muscle cells in the airways, blood vessels, and other tissues. Binding to these receptors activates adenylate cyclase, increases cyclic AMP, and leads to relaxation of smooth muscle, bronchodilation, vasodilation, and increased glycogenolysis. Because of their rapid onset and potency, beta‑2 agonists are among the most widely used drugs for the management of asthma, chronic obstructive pulmonary disease (COPD), and other respiratory disorders. The most common is short‑acting β₂ agonists (SABAs), such as albuterol and levalbuterol, which provide quick relief of bronchospasm. Long‑acting β₂ agonists (LABAs), including salmeterol and formoterol, are delivered via inhalation twice daily and are used as maintenance therapy in combination with inhaled corticosteroids to reduce exacerbations and improve control. A newer class, the ultra‑long‑acting β₂ agonists (ultra‑LABAs), such as vilanterol, offers even longer duration of action. In addition to bronchodilation, β₂ agonists may improve ciliary activity and mucosal blood flow, aiding mucus clearance.

Side effects are typically mild and include tremor, nervousness, tachycardia, and hypokalemia, but systemic exposure is minimized by inhaled delivery. Contraindications include hypersensitivity to any component of the formulation, severe cardiac arrhythmias, and uncontrolled hypertension. Their efficacy can be reduced by tolerance over time; therefore, beta‑2 agonists are often combined with inhaled corticosteroids or leukotriene modifiers for long‑term disease control. The first β₂ agonist, epinephrine, was discovered in the early twentieth century, while modern selective agents were developed in the mid‑twentieth century, revolutionizing respiratory medicine.