Which effect is produced by epinephrine 1:1000 due to agonizing alpha and beta receptors?

• A. Decreased heart rate
• B. Decreased myocardial oxygen demand
• C. Bronchodilation
• D. Vasodilation

Answer: (C)

Epinephrine at 1:1000 acts on both alpha and beta receptors, producing a mix of effects, but the airway effect is driven by beta-2 receptor activation. Activation of beta-2 receptors on bronchial smooth muscle increases cyclic AMP, leading to relaxation of the smooth muscle and bronchodilation, which is the key therapeutic action in conditions like anaphylaxis and bronchospasm.

The other effects described are less consistent with the primary driver here: alpha-1 stimulation causes vasoconstriction, beta-1 increases heart rate and contractility (raising, not lowering, myocardial oxygen demand), and while there can be some beta-2–mediated vasodilation in certain beds, the overall vascular response is not predominantly vasodilation. So the best answer reflects the bronchodilatory effect resulting from beta-2 receptor stimulation.