Notes · Pharmacology · 10 min read
Receptors and drug action
Potency, efficacy and how antagonists change the dose–response curve.
Key points
- Potency is the dose needed for an effect (EC50); efficacy is the maximal effect (Emax).
- A competitive antagonist shifts the curve to the right without lowering Emax.
- A non-competitive antagonist lowers Emax.
- Partial agonists act as antagonists in the presence of a full agonist.
- Therapeutic index = TD50 / ED50; a narrow index needs drug-level monitoring.
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