What is a primary action of epinephrine in acute allergic reactions?

What is a primary action of epinephrine in acute allergic reactions?

• A. Bronchodilation
• B. Bronchoconstriction
• C. No effect on bronchi
• D. Decrease heart rate

Answer: (A)

Epinephrine’s main action in an acute allergic reaction is to open the airways quickly. It does this by stimulating beta-2 receptors on the smooth muscle lining the bronchi, causing the muscles to relax and the airways to dilate. That bronchodilation relieves the wheezing and breathing difficulty that come with anaphylaxis or severe allergic reactions. Epinephrine also helps in other ways, such as causing vasoconstriction through alpha-1 receptors to reduce swelling and support blood pressure, and stimulating the heart via beta-1 receptors to increase heart rate and output. But the most immediate and critical effect for the airway is bronchodilation. Bronchoconstriction would worsen breathing, having no effect on bronchi would be incorrect, and decreasing heart rate is opposite to what epinephrine does.

Epinephrine’s main action in an acute allergic reaction is to open the airways quickly. It does this by stimulating beta-2 receptors on the smooth muscle lining the bronchi, causing the muscles to relax and the airways to dilate. That bronchodilation relieves the wheezing and breathing difficulty that come with anaphylaxis or severe allergic reactions.

Epinephrine also helps in other ways, such as causing vasoconstriction through alpha-1 receptors to reduce swelling and support blood pressure, and stimulating the heart via beta-1 receptors to increase heart rate and output. But the most immediate and critical effect for the airway is bronchodilation.

Bronchoconstriction would worsen breathing, having no effect on bronchi would be incorrect, and decreasing heart rate is opposite to what epinephrine does.