In pharmacology, what term refers to the highest dose at which there is acceptable safety before unacceptable toxicity occurs?

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

Answer: (A)

The term describes the highest dose at which adverse effects are still acceptable and toxicity has not crossed a predefined threshold. In early human trials, drugs are tested at increasing doses until dose-limiting toxicities appear; the largest dose that does not exceed that acceptable level of toxicity is the maximum tolerated dose. This helps define the safety window and informs dosing for later studies. This concept is about safety, not efficacy, which is what the minimum effective dose addresses. The other terms relate to different ideas: lethal dose 50 concerns mortality, and half-life is about how long the drug stays in the body.