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.
Full Agonist Vs Partial Agonist
Mohamad Ali Salloum, PharmD • April 24, 2022
Share
As discussed in previous article, an agonist is a molecule that causes a physiologic response when it binds to its receptor.
A drug can be classified as Full agonist or Partial agonist depending on its efficacy.
Let’s Say Drug A is the Full agonist and Drug B is the partial agonist.
So, how both can be agonists and have different magnitude of action?
A full agonist can be effective 100% although not all receptors are occupied. This means that Drug A needs less than 100% of the receptors to result in full response.
On the other hand, drug B, a partial agonist will never be able to reach 100% even if it occupied 100% of the receptors present.
This happens because the physico-chemical properties of the full agonist that allow it to make a bond with the receptor in a way that it can excite only 3 receptors (theoretically) to result in 100% of the effect.
The physico-chemical properties of the partial agonist allow it to bind to its receptor, however, with lower ability to excite it and produce the desired response, even with occupying 100% of the receptors present.
Examples of full agonists are morphine, opium and phenylephrine. Buprenorphine and Tolazoline are examples of a partial agonist.
You can also watch the illustrative video below for more understanding of the topic.
Resources:
1) R. J. F. R. H. G. Rang HP, Rang and Dale's pharmacology, ed., vol. , , : Elsevier
List of Services
ABOUT THE AUTHOR
Mohamad-Ali Salloum, PharmD
Share
Recent articles:
Low Mood is NOT random!
Learn how CBT rewires thoughts, emotions, and behaviors—and test your knowledge with a quick quiz.
A clear, engaging walkthrough of fentanyl’s pharmacokinetics and pharmacodynamics—from administration to metabolism and excretion—designed for pharmacy and medical students, with visuals, summaries, and an interactive quiz.
Understand Aspirin easily with this blog post.
Learn about Buprenorphine, the strong gripper, but weak pusher 😅
References : American Chemical Society. Tramadol – Molecule of the Week Archive. December 16, 2014. [acs.org] DEA Diversion Control Division. Tramadol Drug & Chemical Evaluation Section Report. April 2025. [deadiversi....usdoj.gov] Grond S, Sablotzki A. Clinical pharmacology of tramadol. Clin Pharmacokinet. 2004;43(13):879‑923. [go.drugbank.com] Food and Drug Administration (FDA). ULTRAM® (tramadol hydrochloride) tablets label. 2004. [accessdata.fda.gov] Nickson C. Tramadol – CCC Pharmacology. Life in the Fast Lane ; 2024. [litfl.com] DrugBank Online. Tramadol: Uses, Interactions, Mechanism of Action. DB00193. [go.drugbank.com] Food and Drug Administration (FDA). Tramadol Hydrochloride Tablets (DailyMed). 2023. [dailymed.nlm.nih.gov] Dean L. Tramadol Therapy and CYP2D6 Genotype. Medical Genetics Summaries . 2015. [ncbi.nlm.nih.gov] Food and Drug Administration (FDA). Tramadol ER Capsules Label Information. 2010. [accessdata.fda.gov] EBM Consult. Mechanism for Tramadol‑Induced Serotonin Syndrome in Patients Taking SSRIs. 2017. Medsafe Pharmacovigilance. Serious Reactions with Tramadol: Seizures and Serotonin Syndrome. 2007. Hassamal S, Miotto K, Dale W, Danovitch I. Tramadol: Understanding the Risk of Serotonin Syndrome and Seizures. Am J Med. 2018;131(11):1382.e1–6. Medscape Reference. Ultram, ConZip (tramadol) dosing, indications, interactions. 2026.
A thoughtful reflection on Declutter Your Mind, exploring mental clutter, awareness, negative thinking patterns, mindfulness, and practical habits for mental clarity.
References: Qiang S, Wu J, Zheng D, et al. The effect of stress mindset on psychological pain: the chain mediating roles of cognitive reappraisal and self-identity. Front Psychol. 2025;16. 1 Bosshard M, Gomez P. Effectiveness of stress arousal reappraisal and stressisenhancing mindset interventions on task performance outcomes: a meta-analysis. Sci Rep. 2024. 2 Zhao S, Chen P, Jin L, et al. Unlocking Emotional Well-Being: Evaluation of a Stress Mindset Intervention With a Metacognitive Approach. Emotion. 2025;25(5):1169–1184. 4 Meyer HH, Stutts LA. The Effect of Mindset Interventions on Stress and Academic Motivation in College Students. Innov High Educ. 2024;49:783–798. 7 Crum AJ, Santoro E, Handley-Miner I, et al. Evaluation of the “Rethink Stress” Mindset Intervention: A Metacognitive Approach to Changing Mindsets. J Exp Psychol Gen. 2023. 3 Laferton JAC, Fischer S, Ebert DD, et al. The Effects of Stress Beliefs on Daily Affective Stress Responses. Ann Behav Med. 2020;54(4):258–267. 5 UCSF Stress Measurement Network. Beliefs about Stress . 2026. 6
References: Qiang S, Wu J, Zheng D, et al. The effect of stress mindset on psychological pain: the chain mediating roles of cognitive reappraisal and self-identity. Front Psychol. 2025;16. 1 Bosshard M, Gomez P. Effectiveness of stress arousal reappraisal and stressisenhancing mindset interventions on task performance outcomes: a meta-analysis. Sci Rep. 2024. 2 Zhao S, Chen P, Jin L, et al. Unlocking Emotional Well-Being: Evaluation of a Stress Mindset Intervention With a Metacognitive Approach. Emotion. 2025;25(5):1169–1184. 4 Meyer HH, Stutts LA. The Effect of Mindset Interventions on Stress and Academic Motivation in College Students. Innov High Educ. 2024;49:783–798. 7 Crum AJ, Santoro E, Handley-Miner I, et al. Evaluation of the “Rethink Stress” Mindset Intervention: A Metacognitive Approach to Changing Mindsets. J Exp Psychol Gen. 2023. 3 Laferton JAC, Fischer S, Ebert DD, et al. The Effects of Stress Beliefs on Daily Affective Stress Responses. Ann Behav Med. 2020;54(4):258–267. 5 UCSF Stress Measurement Network. Beliefs about Stress . 2026. 6
A clear, evidence‑based guide to Ramadan fasting, explaining its metabolic, mental, and cardiometabolic benefits, plus practical nutrition, hydration, sleep, and medication strategies for healthy adults and high‑risk patients.