Median effective dose

ED₅₀

The median effective dose is the dose that produces a quantal effect (all or nothing) in 50% of the population that takes it (median referring to the 50% population base). It is also sometimes abbreviated as the ED₅₀, meaning "effective dose for 50% of the population". The ED₅₀ is commonly used as a measure of the reasonable expectancy of a drug effect, but does not necessarily represent the dose that a clinician might use. This depends on the need for the effect, and also the toxicity. The toxicity and even the lethality of a drug can be quantified by the TD₅₀ and LD₅₀ respectively. Ideally, the effective dose would be substantially less than either the toxic or lethal dose for a drug to be therapeutically relevant.