Which statement best describes high-binding affinity?

Which statement best describes high-binding affinity?

• A. At high concentration, majority of receptors are bound; requires less drug to produce a response
• B. At high concentration, few receptors are bound; requires more drug to produce effect
• C. It measures intrinsic activity
• D. It determines the site of drug action

Answer: (A)

High-binding affinity means the drug binds very tightly to its receptor, so receptor occupancy—and thus the response—can be achieved with a smaller amount of drug. In practical terms, higher affinity lowers the concentration needed to elicit an effect, shifting the dose–response curve to the left. That’s why the description that at high affinity you require less drug to produce a response captures the essence: the binding strength makes it easier to achieve the desired effect without needing large doses. Remember, affinity is about binding strength, not intrinsic activity, and it doesn’t by itself determine where the drug acts.

High-binding affinity means the drug binds very tightly to its receptor, so receptor occupancy—and thus the response—can be achieved with a smaller amount of drug. In practical terms, higher affinity lowers the concentration needed to elicit an effect, shifting the dose–response curve to the left. That’s why the description that at high affinity you require less drug to produce a response captures the essence: the binding strength makes it easier to achieve the desired effect without needing large doses. Remember, affinity is about binding strength, not intrinsic activity, and it doesn’t by itself determine where the drug acts.