Safety of a drug is determined by the degree between which two dose thresholds?

• A. Therapeutic and toxic doses
• B. Lethal dose and effective dose
• C. Minimum effective dose and maximum dose
• D. Onset time and half-life

Answer: (A)

The safety of a drug is best understood by looking at the gap between the dose that produces the desired therapeutic effect and the dose that causes toxicity. This range, often called the therapeutic window or safety margin, shows how much dosing can vary before toxicity occurs. A large gap means a wide margin of safety, while a narrow gap means dosing must be kept precise to avoid harm. The other pairings describe different ideas—how fast a drug acts and how long it stays in the body, or comparing minimum effective dose to a maximum exposure, which aren’t the standard way to assess safety.