beta2selective

Beta2selective refers to pharmacological agents that preferentially interact with the beta-2 adrenergic receptor (β2-AR) over other adrenergic receptor subtypes, particularly beta-1 (β1-AR). These ligands are described as beta-2 selective when their affinity or efficacy at β2 receptors is greater than at β1 or β3 receptors. Selectivity is often relative and dose-dependent, with higher concentrations potentially engaging non-target receptors.

Mechanism of action for β2-selective agonists involves stimulation of the Gs protein–adenylyl cyclase–cAMP pathway. In airway smooth muscle this leads to relaxation and bronchodilation, making such agents useful in conditions like asthma and chronic obstructive pulmonary disease (COPD). They also stabilize mast cells and reduce inflammatory mediator release. In the heart, β2 receptors can contribute to chronotropic and inotropic effects at sufficient doses, so selectivity is not absolute.

Clinical use distinguishes short-acting beta-2 agonists (SABAs) such as albuterol (salbutamol) and terbutaline for rapid relief, from long-acting beta-2 agonists (LABAs) such as salmeterol and formoterol for maintenance therapy. The goal of beta-2 selectivity is to maximize bronchodilation while limiting cardiac effects associated with β1 activation. Potential adverse effects include tremor, tachycardia, palpitations, and, with chronic use, tolerance or reduced responsiveness.

Selectivity is an important concept in drug design and clinical practice, as many beta-agonists vary in their receptor profiles. Non-selective beta agonists or β1-preferring agents can cause more pronounced cardiac effects, underscoring the value of beta-2 selectivity in respiratory indications.