Adrenergic receptor (non-selective, alpha+beta)

Class

Racemic epinephrine (OTC bronchodilator)

Adrenergic receptors are a family of cell-surface proteins that respond to the body's own stress hormones, epinephrine and norepinephrine. They are divided into alpha and beta subtypes, distributed across smooth muscle, the heart, and glands, and they coordinate the acute physiological changes seen during a stress response, including airway widening, blood vessel constriction, and increased heart rate and force of contraction. A non-selective adrenergic agonist activates both alpha and beta receptor families simultaneously, mimicking the natural hormone rather than isolating one branch of this signaling network. Pharmacologically, this rationale matters most in situations demanding a rapid, multi-system correction, such as acute bronchospasm in asthma, where beta-2 receptor activation relaxes airway smooth muscle, or systemic allergic reactions, where combined alpha-mediated vasoconstriction and beta-mediated cardiac and bronchial effects counteract dangerous drops in blood pressure and airway narrowing together. Because the activation is broad rather than tissue-restricted, non-selective agonists produce effects beyond the intended target organ, including cardiovascular stimulation. This mechanism sits at the historical foundation of bronchodilator therapy and remains conceptually important for understanding why later drug development moved toward receptor-subtype-selective agents to reduce off-target cardiac and vascular effects while preserving the desired airway relaxation.