Registered Practical Nurse (RPN) Practice Test

What describes the ability of a drug to produce a biological response after binding to a receptor?

1. Intrinsic activity

2. Affinity

3. Efficacy

4. Biologic action

The correct answer is: Intrinsic activity

The ability of a drug to produce a biological response after binding to a receptor is described by intrinsic activity. This term specifically refers to the inherent capacity of a drug, once it has bound to a receptor, to initiate a response and elicit a physiological effect. It highlights how effectively a drug can activate a receptor and generate a response, distinguishing it from just having the capability to bind to the receptor. While affinity refers to how well a drug binds to its receptor, and efficacy is often used interchangeably with intrinsic activity in some contexts, intrinsic activity specifically denotes the measure of activation once binding has occurred. Biologic action generally encompasses all effects that a drug can have on the body, but it does not directly address the dynamics of receptor binding and response initiation. Understanding intrinsic activity helps in evaluating how different drugs will perform in clinical settings based on their action at receptor sites.