The ED50 (median effective dose) is the dose of a medication that produces a specific effect in 50% of the population that takes that dose. This number has common use as what a clinician or patient can expect for a drug effect, but clinicians may use a different dosage for their particular intended effect, depending on the balance of need or benefit of the drug versus the toxicity of the drug. The toxic dose in 50% of the population is called TD50; the ED50 should hopefully be much less than the TD50, as this would indicate an effective medication at a lower dose.
Kenny BJ, Preuss CV, McPhee AS. ED50. [Updated 2022 Sep 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.