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
Share
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.
List of Services
ABOUT THE AUTHOR
Mohamad-Ali Salloum, PharmD
Share
Recent articles:
Discover how boundaries, autonomy, workload control, and digital disconnection reduce stress, improve recovery, and prevent burnout.
Learn how to recover from burnout by rewiring your brain and nervous system. Discover science-backed techniques including breathwork, mindfulness, exercise, cognitive restructuring, psychological flexibility, and motivation rebuilding.
Learn the science of recovery, why scrolling isn't rest, how sleep repairs the brain, and why weekends alone don't cure burnout.
Burnout is more than stress. Learn how chronic burnout impacts mental health, heart health, immunity, cognition, and overall well-being.
Burnout doesn’t happen overnight. Learn the early warning signs—mental, physical, and behavioral—so you can catch burnout before it takes control.
Feeling exhausted but work isn’t the problem? Learn how life burnout happens and why your daily responsibilities may be draining you.
Think burnout is just stress? Discover how your thoughts, habits, and mindset may be silently driving your exhaustion.
Why do you feel tired but wired? Explore the science of burnout, from cortisol imbalance and HPA axis dysfunction to brain and nervous system changes caused by chronic stress.
Feeling exhausted even after rest? Learn what burnout is, its warning signs, causes, and how it differs from stress and depression. Understand why burnout is increasing and who is most at risk.
References: Dhabhar FS. Effects of stress on immune function: the good, the bad, and the beautiful. Immunol Res. 2014;58(2–3):193–210. [link.springer.com] Tang L, Cai N, Zhou Y, et al. Acute stress induces an inflammation dominated by innate immunity represented by neutrophils. Front Immunol. 2022;13:1014296. [pmc.ncbi.nlm.nih.gov] Alotiby A. Immunology of stress: a review article. J Clin Med. 2024;13(21):6394. [mdpi.com] Haykin H, Rolls A. The neuroimmune response during stress: a physiological perspective. Immunity. 2021;54(9):1933–1947. [cell.com] Gutierrez Nunez S, et al. Chronic stress and autoimmunity: the role of HPA axis and cortisol dysregulation. Int J Mol Sci. 2025;26(20):9994. [pmc.ncbi.nlm.nih.gov] Bae YS, Shin EC. Editorial: Stress and immunity. Front Immunol. 2019;10:245. [pmc.ncbi.nlm.nih.gov]