In dose-ranging pharmacology studies, which term defines the highest dose with acceptable safety before toxicity occurs?

• A. Lethal dose 50
• B. Maximum tolerated dose (MTD)
• C. Minimum effective dose
• D. Half-life

Answer: (B)

The highest dose with acceptable safety before toxicity occurs is the maximum tolerated dose. In dose-ranging studies, researchers gradually increase the dose until dose-limiting toxicities appear; the largest dose that remains tolerable without unacceptable adverse effects is defined as the maximum tolerated dose, which helps set the upper limit for safe dosing in later trials and informs the therapeutic window.

Other terms don’t fit this concept: LD50 is a lethal-dose measure used in toxicology to indicate the dose that would kill 50% of subjects, not tolerability; the minimum effective dose is the smallest dose that produces the desired effect, focusing on efficacy rather than safety; and half-life is the time it takes for the drug’s concentration to fall by half, which relates to pharmacokinetics rather than the safety boundary.