Two antihypertensive agents are tested in healthy volunteers. Drug A lowers mean arterial pressure by a maximum of 15 mmHg with an EC50 of 1 mg/day. Drug B lowers it by a maximum of 30 mmHg with an EC50 of 10 mg/day. Which conclusion is correct?
- A Drug A is more efficacious than drug B
- B Drug A is more potent, and drug B is more efficacious ✓
- C Drug B is more potent than drug A
- D Both drugs have equal potency and equal efficacy
Correct answer: B. Drug A is more potent, and drug B is more efficacious
Explanation
Potency reflects the dose needed to produce a given effect and is read from position along the dose axis, indicated here by EC50. Drug A achieves its effects at a tenfold lower dose, so it is more potent. Efficacy reflects the maximum achievable effect, the plateau of the graded dose-response curve. Drug C reaches twice the maximal blood pressure fall, so it is more efficacious. Clinically, efficacy usually matters more than potency when choosing between drugs.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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