Which term describes the effective dose for 50% of the population (ED50)?

• A. Toxic dose for 50% of population
• B. Peak level
• C. Onset time
• D. Effective dose for 50% of the population

Answer: (D)

The main idea is understanding what ED50 means. ED50 is the amount of a drug that produces the defined therapeutic effect in 50% of the population. It comes from the dose–response curve and reflects potency: a smaller ED50 means the drug is more potent because a lower dose achieves the effect in half the people. This term is specifically about effective, not toxic or lethal, responses. It isn’t about how high the drug concentration peaks in the blood (peak level) or how quickly the effect begins (onset time). It also isn’t the dose that causes toxicity in half the population (that would be TD50). So the phrase “effective dose for 50% of the population” correctly identifies ED50.