Affinity, potency and efficacy: three different terms
Greater potency in an assay does not automatically make a molecule a better treatment.
A short vocabulary for reading molecular comparisons.
Greater potency in an assay does not automatically make a molecule a better treatment.
Three questions
Affinity describes the binding interaction with a target. Potency expresses the concentration or dose needed to produce a defined effect. Pharmacological efficacy concerns the ability to produce a response; the observed maximum also depends on the system. The terms answer related but different questions.
Using the vocabulary
Before comparing two numbers, ask whether they come from the same assay and response. EC50 and Kd are not synonyms. In this context, pharmacological efficacy also differs from demonstrated clinical benefit in patients.
Professional context / Contexto profesional
Receptor reserve, coupling and assay conditions can affect the relationship between binding and response.
Evidence / Evidencia
Educational synthesis, not a product-ranking scale.
Limitations / Limitaciones
The definitions require experimental context and provide no dose-conversion rule.