Which vasopressor increases systemic blood pressure indirectly by releasing norepinephrine from sympathetic nerve fibers and directly by binding to adrenergic receptors?

Which vasopressor increases systemic blood pressure indirectly by releasing norepinephrine from sympathetic nerve fibers and directly by binding to adrenergic receptors?

• A. Dobutamine
• B. Ephedrine
• C. Epinephrine
• D. Phenylephrine

Answer: (B)

Ephedrine is a mixed-acting vasopressor that increases blood pressure through two simultaneous actions: it releases endogenous norepinephrine from sympathetic nerve terminals (indirect effect) and it directly stimulates adrenergic receptors (direct effect). The indirect release adds sympathetic tone and vasoconstriction, while the direct receptor activation, especially at alpha-1 on vessels and beta receptors on the heart, boosts vascular tone and cardiac output. Other options either act mainly by direct receptor stimulation (epinephrine, phenylephrine) or primarily as a beta-1 agonist without the NE-release mechanism (dobutamine). This combination of indirect NE release plus direct receptor activation is why ephedrine fits the description.

Ephedrine is a mixed-acting vasopressor that increases blood pressure through two simultaneous actions: it releases endogenous norepinephrine from sympathetic nerve terminals (indirect effect) and it directly stimulates adrenergic receptors (direct effect). The indirect release adds sympathetic tone and vasoconstriction, while the direct receptor activation, especially at alpha-1 on vessels and beta receptors on the heart, boosts vascular tone and cardiac output. Other options either act mainly by direct receptor stimulation (epinephrine, phenylephrine) or primarily as a beta-1 agonist without the NE-release mechanism (dobutamine). This combination of indirect NE release plus direct receptor activation is why ephedrine fits the description.