Certified Registered Nurse Anesthetist (CRNA) Practice Exam

What is the mechanism of action for epinephrine?

1. Inhibits phosphodiesterase

2. Inhibits calcium reuptake

3. Direct-acting alpha and beta agonist

4. Serves as a competitive antagonist

The correct answer is: Direct-acting alpha and beta agonist

Epinephrine's mechanism of action as a direct-acting alpha and beta agonist is crucial for its role in the body. As both an alpha and beta receptor agonist, epinephrine stimulates alpha-1 adrenergic receptors, leading to vasoconstriction, which increases systemic vascular resistance and blood pressure. Simultaneously, it interacts with beta-1 adrenergic receptors in the heart, enhancing heart rate and contractility, which boosts cardiac output. Furthermore, its action on beta-2 adrenergic receptors results in bronchodilation and relaxation of smooth muscles, particularly in the airways, making it an essential medication for conditions such as asthma and anaphylaxis. This dual action of stimulating both types of adrenergic receptors allows epinephrine to be effective in a variety of clinical scenarios, especially in emergency situations where rapid cardiovascular support and bronchodilation are needed. The understanding of its mechanism is fundamental for CRNA professionals, as it underlines why epinephrine is often a first-line treatment in acute allergic reactions and cardiac arrest situations.