Betaagonistit

Betaagonistit are a class of drugs that stimulate beta-adrenergic receptors in the body. They act by activating Gs proteins and increasing cyclic adenosine monophosphate (cAMP) via adenylate cyclase, which leads to various physiological effects depending on the receptor subtype engaged.

Most clinically used beta-agonists target the beta-2 receptors in airway smooth muscle to produce bronchodilation. They can be broadly categorized by duration of action: short-acting beta-agonists (SABA) such as salbutamol (albuterol) and terbutaline provide rapid relief of bronchospasm; long-acting beta-agonists (LABA) such as salmeterol and formoterol offer sustained relief for maintenance therapy. There are also beta-3 agonists, such as mirabegron, used for symptoms of overactive bladder; these have different primary indications from respiratory beta-agonists and are not used for acute bronchospasm.

Clinical uses include relief of acute bronchospasm in asthma and chronic obstructive pulmonary disease (COPD), prevention of exercise-induced bronchoconstriction, and, in emergency settings, epinephrine (a non-selective beta-adrenergic agonist) is used for anaphylaxis. In obstetrics, terbutaline has been used as a tocolytic to delay preterm labor. In bladder medicine, beta-3 agonists are used to treat overactive bladder, illustrating the receptor-specific diversity of the class.

Administration routes vary by indication. Inhaled formulations deliver targeted action to the lungs with fewer systemic effects; oral or intravenous forms are used for other indications. Onset and duration depend on the specific agent and preparation. Side effects commonly include tachycardia, tremor, nervousness, and palpitations; systemic use can cause tachyarrhythmias, hyperglycemia, and electrolyte shifts such as hypokalemia. Cautions include interactions with beta-blockers and, for asthma, avoiding LABA monotherapy in favor of combination therapy with inhaled corticosteroids.