What term describes a small range between effective and toxic drug levels?

The term that describes a small range between effective and toxic drug levels is the Narrow Therapeutic Index. This indicates that there is a minimal margin of safety between the dose that produces the desired therapeutic effect and the dose that causes toxicity. Medications with a narrow therapeutic index require careful monitoring and precise dosing to avoid adverse effects and ensure efficacy. Examples of such drugs include warfarin and lithium, where even slight changes in dose or blood levels can lead to serious clinical consequences. Understanding the concept of a narrow therapeutic index is crucial for healthcare professionals to prevent potential harm to patients while managing their medications effectively.