Which class increases blood pressure by constricting vessels and is used to treat severe allergic reactions?

• A. Vasodilator
• B. Vasopressor
• C. Antihistamine
• D. Anxiolytic

Answer: (B)

Vasopressors increase blood pressure by constricting blood vessels, rapidly counteracting the vasodilation and fluid leakage that occur in a severe allergic reaction (anaphylaxis). The prototypical example used in this scenario is epinephrine, which works on alpha-adrenergic receptors to constrict peripheral vessels (raising systemic vascular resistance and BP) and on beta-adrenergic receptors to support heart output and open airways. This combination addresses both the life-threatening drop in blood pressure and the bronchoconstriction that can accompany anaphylaxis.

Vasodilators would worsen hypotension by widening vessels, so they’re unsuitable. Antihistamines address allergic symptoms like itching and hives but don’t rapidly reverse life-threatening hypotension or airway compromise. Anxiolytics don’t target the acute pathophysiology of anaphylaxis either.