Mohamad-Ali Salloum is a Pharmacist and science writer. He loves simplifying science to the general public and healthcare students through words and illustrations. When he's not working, you can usually find him in the gym, reading a book, or learning a new skill.
Efficacy Vs Potency
Mohamad Ali Salloum, PharmD • March 6, 2022
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What are they and what do we need to know about these two concepts?
First let’s define them.
Efficacy is the ability of a drug to elicit a physiologic response when it interacts with a receptor.
Potency is the amount of drug needed to produce a certain response.
Two drugs can have the same effectiveness but different potencies.
Let’s suppose we have 2 dugs, Drug A and Drug B.
Drug A induces a 70% effect with only 3 molecules.
Drug B induces the same 70% effect with 6 molecules.
This means that both has the same efficacy, but Drug A is more potent than Drug B.
Knowing the difference in potency between drugs allows us to have several options for treating a patient and achieving the same clinical results.
Note that some drugs (let’s say Drug C) can’t reach the 70%, and when used in their maximal concentration they may reach 50% effect. In comparison with both Drugs A and B, Drug C is considered less effective.
For example, when comparing the corticosteroids (as shown in the table below), we find that dexamethasone is the most potent in terms of anti-inflammatory effect. However, all of the below corticosteroids can achieve the same efficacy when used at the appropriate calculated doses.
You can also watch the illustrative video below for more understanding of the topic.
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ABOUT THE AUTHOR
Mohamad-Ali Salloum, PharmD
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References: Quattash MS. The Depleted Mind: The Science of Decision Fatigue and Ego Depletion. Global Council for Behavioral Science. 2025. Available from: https://gc-bs.org/articles/the-depleted-mind-the-science-of-decision-fatigue-and-ego-depletion/ 5 Choudhury NA, Saravanan P. An integrative review on the causes and effects of decision fatigue. Front Cognit. 2026;4:1719312. Available from: https://www.frontiersin.org/journals/cognition/articles/10.3389/fcogn.2025.1719312/full 4 Schweitzer DR, Baumeister RF, Laakso EL, Ting J. Self-control, limited willpower and decision fatigue in healthcare settings. Intern Med J. 2023. Available from: https://onlinelibrary.wiley.com/doi/pdf/10.1111/imj.16121 3 Ordali E, Pietrini P. Mental fatigue leads to loss of self-control and poor decision-making. Coverage in The Brighter Side of News. 2024. Available from: https://www.thebrighterside.news/post/mental-fatigue-leads-to-loss-of-self-control-and-poor-decision-making/ 2 Woodley BioReg. Decision Fatigue and Cognitive Load: A Scientific Perspective. Woodley BioReg. 2026. Available from: https://www.woodleybioreg.com/decision-fatigue-and-cognitive-load-a-scientific-perspective/ 1 Keller AJ. Decision Fatigue: What It Is and How It Affects Your Brain. Neurosity Guide. 2026. Available from: https://neurosity.co/guides/decision-fatigue-brain
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