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Pharmacology · single question

On a dose-response curve graphic showing two drugs (Drug A and Drug B), Drug A produces a 50% maximal effect (EC50) at a LOWER dose than Drug B. Which drug is MORE potent?

  1. Drug B (requires higher dose for same effect)
  2. Drug A (requires lower dose for same effect)
  3. Both are equally potent if they reach the same maximum effect
  4. Potency cannot be determined from a dose-response curve
Show answer and explanation

Correct answer: B. Drug A (requires lower dose for same effect)

Potency refers to the amount of drug needed to produce a given effect — a more potent drug achieves its effect at a LOWER dose (lower EC50). Drug A, which produces its effect at a lower dose, is MORE potent. Note: potency is different from efficacy (maximum effect achievable). Drug B might be equally or more efficacious (if it reaches a higher maximum effect) but is LESS potent. Left-shifted curves = more potent.

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