Binding affinity is best described as what?

Binding affinity is best described as what?

• A. A measure of the attraction force between the receptor and the drug
• B. The rate of drug metabolism
• C. The time to onset of action
• D. The distribution of drug in tissues

Answer: (A)

Binding affinity is the strength of the interaction between the receptor and the drug at equilibrium—how tightly the drug binds. It’s described by how much drug is needed to occupy receptors (lower Kd means higher affinity), so at a given concentration more of the receptor is bound when affinity is high. This property focuses on the receptor–drug interaction itself, not what happens after binding. It’s different from how quickly a drug is metabolized, how soon its effects begin, or how it distributes in tissues, which are pharmacokinetic or other pharmacodynamic aspects. So the best description is that binding affinity measures the attraction/interaction strength between the receptor and the drug.

Binding affinity is the strength of the interaction between the receptor and the drug at equilibrium—how tightly the drug binds. It’s described by how much drug is needed to occupy receptors (lower Kd means higher affinity), so at a given concentration more of the receptor is bound when affinity is high. This property focuses on the receptor–drug interaction itself, not what happens after binding. It’s different from how quickly a drug is metabolized, how soon its effects begin, or how it distributes in tissues, which are pharmacokinetic or other pharmacodynamic aspects. So the best description is that binding affinity measures the attraction/interaction strength between the receptor and the drug.