Core6: Efficacy, potency

📈 High-yield / 要点：Potency = dose/concentration needed; efficacy = maximal effect. They are independent.

Potency / 力価

• Potency describes the concentration or dose required to produce a given effect.
• Common comparison point: EC50 = concentration producing 50% of maximal effect.
• Lower EC50 → less drug needed → higher potency.
• On a concentration-response curve:
  • More potent drug is shifted left.
  • If two curves have the same maximum height, they have the same efficacy.

Efficacy / 有効性・効力

• Efficacy is the maximal effect / Emax an agonist can produce.
• It reflects how well the drug can produce a response, not how much drug is needed.
• On a concentration-response curve:
  • Higher efficacy = higher maximum height of the curve.
  • A drug may be less potent but more efficacious, or more potent but less efficacious.

Comparison / 比較

Parameter	Meaning	Curve feature	Key phrase
Potency	How much drug is needed	Left-right position; EC50	Lower EC50 = more potent
Efficacy	How strong the maximal effect is	Maximum height; Emax	Higher Emax = more efficacious

Curve interpretation / 曲線の読み方

• A vs B with parallel curves and same Emax：
  • Same efficacy.
  • Left-shifted curve has higher potency.
  • Parallel slopes suggest action at the same receptor system.
• X vs Y with different Emax：
  • Higher curve has higher efficacy.
  • If also left-shifted, it has higher potency too.

Remember / 覚え方

• Potency = position on x-axis.
• Efficacy = height on y-axis.
• Potent ≠ necessarily more effective.