Efficacy
Also known as: intrinsic activity · maximal effect
The maximum effect a compound can produce once bound — distinct from potency, which is the dose needed to get there.
Efficacy is the size of the maximum response a compound can produce at its target, no matter how much is present. A full agonist has high efficacy; a partial agonist produces only a submaximal effect even when every receptor is occupied.
Efficacy and potency are often confused but answer different questions: efficacy is "how big an effect is possible?", potency is "how much is needed to get an effect?". Both shape how a research compound is characterised.
RELATED TERMS
Potency (Pharmacology)
The amount of a compound needed to produce a given effect — a more potent compound works at a lower dose.
Receptor / Agonist
A receptor is a cell’s signal-receiving protein; an agonist binds it and activates it, an antagonist blocks it.
Binding Affinity
How tightly a molecule binds its target receptor — a key measure of how potent and selective a compound is.
Selectivity
How specifically a compound acts on its intended target and few others — the basis of a "clean" research effect.
Educational content, not medical advice. All products supplied for research purposes only — not for human consumption.