What does the therapeutic index represent?

The therapeutic index is a critical concept in pharmacology that quantifies the safety and efficacy of a drug. Specifically, it represents the ratio of the dose required to produce a desired therapeutic effect to the dose that causes toxicity or death in 50% of subjects. In essence, it provides a measure of the margin of safety of a drug; a higher therapeutic index indicates a safer drug, as there is a larger difference between effective and toxic doses. This ratio is vital for determining appropriate dosing and ensuring patient safety during treatment.

Understanding the therapeutic index helps clinicians and researchers evaluate and compare drugs, making it easier to predict potential side effects and establish safe dosage ranges. This assessment is especially important in situations where the therapeutic window is narrow, meaning the effective dose is close to the toxic dose.