ED50 is defined as the dose that causes what in a group of subjects?

ED50 stands for the "effective dose" at which 50% of a given population experiences a specified effect from a drug or treatment. This dose is essential for understanding the relationship between the dose of a substance and its pharmacological effects within a population.

In the context of pharmacology and toxicology, the term "effects" can encompass a range of outcomes, such as therapeutic effects, adverse effects, or other measurable responses. The significance of the ED50 lies in its application for determining the efficacy of a drug; by knowing how much of a substance is required to elicit a response in half the subjects, clinicians and researchers can better gauge dosages for therapeutic applications and assess potential risks in treatments.

The other options do not align with the definition of ED50. For example, maximum safe exposure refers to a threshold beyond which toxicity may occur, while severe adverse reactions in all subjects would imply a uniform and negative outcome not captured by the concept of ED50. Similarly, full recovery in all subjects does not reflect a statistical measure of effects within a population, as ED50 does not require all individuals to respond identically. Thus, the definition of ED50 accurately captures the intended meaning of its role in assessing drug effects within a population.