FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam

What does the term EC50 refer to in pharmacology?

1. Concentration of the drug that produces 50% of maximal effect

2. The dose that kills half of the test group

3. Amount of drug to produce toxic effects in 50% of the population

4. The therapeutic response produced in 50% of the test group

The correct answer is: Concentration of the drug that produces 50% of maximal effect

The term EC50 refers to the "Effective Concentration 50," which is defined as the concentration of a drug that produces 50% of its maximal effect. This metric is crucial in pharmacology as it provides insight into the potency of a drug. A lower EC50 value indicates that a smaller amount of the drug is required to achieve half of the maximum effect, which can suggest a higher potency. In therapeutic contexts, understanding the EC50 can help in determining appropriate dosing and assessing the drug's effectiveness in comparison to other medications. It is particularly useful when evaluating dose-response relationships, as it provides a quantifiable measure to compare how different drugs work across various conditions or populations. The other options relate to different pharmacological concepts, like lethal doses (which pertain to toxicology) or therapeutic responses, but they do not accurately define EC50. Thus, the focus on achieving 50% of the maximum effect distinctly positions EC50 within the framework of drug efficacy.