Question:easy
The graph below shows the dose-response curves of three drugs A, B and C. Which of the following drugs shown in the graph has the highest potency?
The graph below shows the dose-response curves of three drugs A, B and C. Which of the following drugs shown in the graph has the highest potency?
Show Hint
Potency is about how far left the curve sits, not how high it rises.
Updated On: Jun 23, 2026
- Drug A
- Drug B
- Drug C
- Both Drug A & B
Show Solution
The Correct Option is A
Solution and Explanation
Separate the two concepts first. Potency is a horizontal property: how far left the dose-response curve lies, set by the EC50. Efficacy is a vertical property: the maximal height the curve can reach. The question asks for potency, so only left-right position matters.
The rule: leftmost curve equals lowest EC50 equals highest potency, because a smaller dose achieves the half-maximal effect. A curve shifted right needs more drug for the same response and is therefore less potent.
On this graph Drug A is the leftmost curve, so it has the smallest $EC_{50}$ and the greatest potency. Option (d) is wrong because A and B do not share the same curve position, and C lies furthest right. The answer is option (a), Drug A.
The rule: leftmost curve equals lowest EC50 equals highest potency, because a smaller dose achieves the half-maximal effect. A curve shifted right needs more drug for the same response and is therefore less potent.
On this graph Drug A is the leftmost curve, so it has the smallest $EC_{50}$ and the greatest potency. Option (d) is wrong because A and B do not share the same curve position, and C lies furthest right. The answer is option (a), Drug A.
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