CEA Nursing Practice Exam

Which concept indicates that small differences in dose may lead to serious therapeutic failures?

1. Narrow therapeutic index

2. Wide therapeutic index

3. Post-antibiotic effect

4. Zero order kinetics

The correct answer is: Narrow therapeutic index

The concept that small differences in dose may lead to serious therapeutic failures is referred to as a narrow therapeutic index. This term is used in pharmacology to describe drugs for which the range between the minimum effective dose and the minimum toxic dose is very small. Consequently, minor variations in dosage or blood concentration can result in significant therapeutic failures, such as insufficient efficacy or adverse drug reactions. Drugs with a narrow therapeutic index require careful monitoring to ensure that the therapeutic levels are achieved without exceeding toxic levels. Examples of such drugs include warfarin, lithium, and certain anticonvulsants. The need for precise dosing and monitoring highlights the critical importance of understanding this concept in nursing practice to prevent medication errors and ensure patient safety. In contrast, a wide therapeutic index indicates a greater margin of safety in dosing, where fluctuations in doses are less likely to lead to severe consequences. The post-antibiotic effect refers to the continued suppression of bacterial growth after antibiotic levels fall below the minimum inhibitory concentration, which is unrelated to dose variability. Zero order kinetics describes a situation where the drug elimination rate is constant regardless of drug concentration, again not related to the concept of dose differences leading to therapeutic failure.