Pharmacology · single question
In a dose-response curve showing Drug A and Drug B, Drug A reaches the same maximum effect but at a LOWER concentration. Which drug is MORE POTENT?
Show answer and explanation
Correct answer: A. Drug A (reaches EC50 at lower concentration)
Drug A is more potent (A). Potency refers to the amount of drug required to produce a given effect — specifically the EC50 (concentration producing 50% of maximum effect).
• More potent = lower EC50 = less drug needed for the same effect.
• Drug A has a lower EC50 (its curve is shifted to the LEFT on the concentration axis) → MORE POTENT.
• Efficacy vs. Potency:
- Efficacy: the MAXIMUM EFFECT a drug can produce (Emax) — both drugs reach the same Emax → equal efficacy.
- Potency: how much drug is needed to produce a given effect → Drug A is more potent.
• Clinical implication: a more potent drug does NOT necessarily mean a better or more efficacious drug — it just means you need less of it.
• More potent = lower EC50 = less drug needed for the same effect.
• Drug A has a lower EC50 (its curve is shifted to the LEFT on the concentration axis) → MORE POTENT.
• Efficacy vs. Potency:
- Efficacy: the MAXIMUM EFFECT a drug can produce (Emax) — both drugs reach the same Emax → equal efficacy.
- Potency: how much drug is needed to produce a given effect → Drug A is more potent.
• Clinical implication: a more potent drug does NOT necessarily mean a better or more efficacious drug — it just means you need less of it.