Which term describes the maximal efficacy of a drug?

Which term describes the maximal efficacy of a drug?

• A. Potency
• B. TI
• C. EC50
• D. Emax

Answer: (D)

Maximal efficacy is about the highest effect a drug can produce, regardless of dose. This ceiling effect is captured by Emax, which reflects the intrinsic ability of the drug–receptor system to generate a response. Full agonists can drive the response up to this maximum, while partial agonists reach a lower ceiling. Potency describes how much drug is needed to reach a given level of effect, not the maximum, and EC50 is the concentration needed for half of the maximal effect. TI is a safety measure, not about how strong the drug’s effect can be. So the term that describes the maximal efficacy is Emax.

Maximal efficacy is about the highest effect a drug can produce, regardless of dose. This ceiling effect is captured by Emax, which reflects the intrinsic ability of the drug–receptor system to generate a response. Full agonists can drive the response up to this maximum, while partial agonists reach a lower ceiling. Potency describes how much drug is needed to reach a given level of effect, not the maximum, and EC50 is the concentration needed for half of the maximal effect. TI is a safety measure, not about how strong the drug’s effect can be. So the term that describes the maximal efficacy is Emax.