Epinephrine acts on which receptor subtypes?

Epinephrine acts on which receptor subtypes?

• A. Alpha-1, Beta-1, Beta-2
• B. Alpha-1, Alpha-2, Beta-1, Beta-2
• C. Alpha-2, Beta-1, Beta-2
• D. Beta-1, Beta-2

Answer: (B)

Epinephrine is a nonselective adrenergic agonist, meaning it activates both alpha and beta receptors. It binds to alpha-1, alpha-2, beta-1, and beta-2 receptors. This broad receptor engagement explains its mixed effects: beta-1 increases heart rate and contractility; beta-2 causes bronchodilation and some vasodilation in skeletal muscle; alpha-1 promotes vasoconstriction to raise blood pressure; alpha-2 helps modulate norepinephrine release and other autonomic effects. Because it acts on all four subtypes, this is why its clinical actions include both cardiovascular stimulation and airway/vascular effects. Other agents are more selective and do not engage all four, whereas epinephrine’s profile covers them all.

Epinephrine is a nonselective adrenergic agonist, meaning it activates both alpha and beta receptors. It binds to alpha-1, alpha-2, beta-1, and beta-2 receptors. This broad receptor engagement explains its mixed effects: beta-1 increases heart rate and contractility; beta-2 causes bronchodilation and some vasodilation in skeletal muscle; alpha-1 promotes vasoconstriction to raise blood pressure; alpha-2 helps modulate norepinephrine release and other autonomic effects. Because it acts on all four subtypes, this is why its clinical actions include both cardiovascular stimulation and airway/vascular effects. Other agents are more selective and do not engage all four, whereas epinephrine’s profile covers them all.