Registered Practical Nurse (RPN) Practice Test

What is the term for the strength of the bond between a drug and its receptor?

1. Affinity

2. Efficacy

3. Potency

4. Activity

The correct answer is: Affinity

The term that describes the strength of the bond between a drug and its receptor is affinity. Affinity refers to how readily a drug can bind to a receptor, which is crucial in pharmacology as it impacts the drug’s effectiveness and overall therapeutic use. A drug with high affinity will bind more tightly and effectively to its target receptor, potentially leading to stronger or more sustained therapeutic effects. In contrast, efficacy refers to the maximum effect a drug can produce, regardless of how well it binds. Potency indicates the amount of drug needed to produce a given effect, which is related but distinct from the strength of the bond with the receptor. Activity often describes the biological effect resulting from drug-receptor interaction but does not specifically address the strength of the bond itself. Understanding these distinctions helps clarify how drugs function and their interactions within the body.