Which agent acts as an alpha-1 and beta-1 adrenergic agonist?

Which agent acts as an alpha-1 and beta-1 adrenergic agonist?

• A. Epinephrine
• B. Pseudoephedrine
• C. Isoproterenol
• D. Norepinephrine

Answer: (D)

Norepinephrine is a direct adrenergic agonist with predominant effects on alpha-1 and beta-1 receptors, and very little action at beta-2 receptors. Activating alpha-1 receptors in vascular smooth muscle causes vasoconstriction, which raises systemic vascular resistance and blood pressure. Simultaneously, stimulating beta-1 receptors in the heart increases contractility (inotropy) and, to a lesser degree, heart rate (chronotropy), boosting cardiac output. Because beta-2 activity is minimal, there isn’t significant bronchodilation or skeletal muscle vasodilation, so the net effect is mainly vasoconstriction plus increased cardiac work. In contrast, other agents either spare alpha-1, rely on beta-2, or act indirectly. Epinephrine hits alpha-1, beta-1, and beta-2 (so it has broad effects including vasodilation via beta-2), isoproterenol is a beta-agonist with little alpha-1 activity, and pseudoephedrine mainly works by releasing norepinephrine indirectly with milder direct receptor activity.

Norepinephrine is a direct adrenergic agonist with predominant effects on alpha-1 and beta-1 receptors, and very little action at beta-2 receptors. Activating alpha-1 receptors in vascular smooth muscle causes vasoconstriction, which raises systemic vascular resistance and blood pressure. Simultaneously, stimulating beta-1 receptors in the heart increases contractility (inotropy) and, to a lesser degree, heart rate (chronotropy), boosting cardiac output. Because beta-2 activity is minimal, there isn’t significant bronchodilation or skeletal muscle vasodilation, so the net effect is mainly vasoconstriction plus increased cardiac work.

In contrast, other agents either spare alpha-1, rely on beta-2, or act indirectly. Epinephrine hits alpha-1, beta-1, and beta-2 (so it has broad effects including vasodilation via beta-2), isoproterenol is a beta-agonist with little alpha-1 activity, and pseudoephedrine mainly works by releasing norepinephrine indirectly with milder direct receptor activity.