Beta2agonister

Beta2agonister, also written beta-2 agonists, are medications that selectively stimulate beta-2 adrenergic receptors in smooth muscle. They are used primarily to treat airway constriction in asthma and chronic obstructive pulmonary disease (COPD) and can be administered for rapid relief or longer-term control. Some older uses have included tocolysis in obstetric settings, though this practice has become limited due to safety concerns.

Mechanism of action: Beta2agonister activate Gs protein-coupled beta-2 receptors, increasing cyclic AMP in smooth muscle cells. This leads to relaxation of bronchial smooth muscle, bronchodilation, and inhibition of mediator release from mast cells. The result is reduced airway resistance and decreased hyperresponsiveness.

Pharmacology and administration: Inhalation is the preferred route to maximize local effect and minimize systemic exposure. Short-acting beta-2 agonists (SABAs) such as albuterol (salbutamol) provide rapid bronchodilation within minutes and last about 4–6 hours. Long-acting beta-2 agonists (LABAs) such as salmeterol and formoterol offer extended bronchodilation (often 12 hours or more) and may have a rapid onset (formoterol) but are generally paired with inhaled corticosteroids for asthma management.

Clinical use: Beta2agonister are used for relief of acute bronchoconstriction and for long-term control in asthma and COPD. LABAs are recommended as part of combination therapy with inhaled corticosteroids in persistent asthma and should not be used alone. They can also be used for exercise-induced bronchoconstriction prophylaxis in some patients.

Adverse effects and safety: Common systemic effects include tremor, tachycardia, palpitations, and headache. Skeletal muscle tremor and minor heart rate increases are more likely with inhaled or systemic exposure at higher doses. Long-term use requires monitoring for tolerance and appropriate dosing to minimize risks.