Registered Practical Nurse (RPN) Practice Test

What term refers to the ability of a drug to produce a desired therapeutic response?

1. Affinity

2. Efficacy

3. Potency

4. Activity

The correct answer is: Efficacy

The ability of a drug to produce a desired therapeutic response is referred to as efficacy. Efficacy describes the maximum effect that a drug can produce when it binds to its target receptor or site of action. It is an essential concept in pharmacology because it helps determine how well a medication can achieve the intended therapeutic goal, such as pain relief, reduction of blood pressure, or improvement of a condition. In contrast, affinity refers to how well a drug can bind to its receptor; it speaks to the strength of the interaction between the drug and the receptor. While high affinity can certainly contribute to a drug's efficacy, it does not guarantee that the drug will produce a significant therapeutic effect once bound. Potency, on the other hand, describes the amount of drug needed to achieve a specific effect. A highly potent drug requires a smaller dose to elicit a response compared to a less potent drug. However, potency does not necessarily indicate the overall therapeutic effectiveness of the drug. Activity generally refers to the actual functioning or action of the drug within the system but is broader than the specific desired therapeutic effect. Therefore, while it may encompass various aspects of drug performance, efficacy specifically pinpoints the desired outcome produced by the drug.