Which statement best describes low-binding affinity?

Which statement best describes low-binding affinity?

• A. At high concentration, few receptors are bound; requires more drug to produce effect
• B. At high concentration, majority of receptors are bound; requires less drug to produce a response
• C. It measures selectivity
• D. It is determined by receptor distribution

Answer: (A)

Binding affinity is how tightly a drug binds to its receptor, and it directly influences potency. When a drug has low affinity, it doesn’t bind strongly, so you need much higher concentrations to achieve meaningful receptor occupancy and produce an effect. That’s why the statement describing low affinity notes that at high concentration only a small fraction of receptors are bound and you require more drug to get a response—the occupancy is slow to rise and the effect requires more drug to be reached. The other ideas aren’t about affinity: affinity doesn’t measure selectivity, and it isn’t determined by where receptors are distributed in the body.

Binding affinity is how tightly a drug binds to its receptor, and it directly influences potency. When a drug has low affinity, it doesn’t bind strongly, so you need much higher concentrations to achieve meaningful receptor occupancy and produce an effect. That’s why the statement describing low affinity notes that at high concentration only a small fraction of receptors are bound and you require more drug to get a response—the occupancy is slow to rise and the effect requires more drug to be reached. The other ideas aren’t about affinity: affinity doesn’t measure selectivity, and it isn’t determined by where receptors are distributed in the body.