What is the mechanism of action of epinephrine 1:1000?

• A. Stimulates Alpha and Beta Adrenergic receptors
• B. Causes vasodilation and decreased heart rate
• C. Inhibits platelet aggregation
• D. Blocks acetylcholine receptors

Answer: (A)

Epinephrine 1:1000 works by nonselectively activating both alpha and beta adrenergic receptors. Activation of alpha-1 receptors on vascular smooth muscle causes vasoconstriction, which raises blood pressure and reduces mucosal edema in the airways. Activation of beta-1 receptors in the heart increases heart rate and the force of contraction, boosting cardiac output. Activation of beta-2 receptors in bronchial smooth muscle produces bronchodilation, easing bronchospasm. When given intramuscularly for anaphylaxis, these combined effects rapidly counter airway compromise and hypotension. The described actions—vasoconstriction, increased heart rate/contractility, and bronchodilation—fit the mechanism of epinephrine best, whereas the other options describe effects epinephrine does not primarily produce (vasodilation with bradycardia, platelet aggregation inhibition, or acetylcholine receptor blockade).