ED90

ED90 is a pharmacological term used to denote the dose or concentration of a drug that produces 90% of the maximal effect (Emax) in a given biological system or population. It is a point on the dose–response curve that is higher than the median effective dose (ED50) and is frequently used to express potency and dosing requirements, especially when a higher efficacy target is needed or when safety margins are considered.

Calculation and interpretation often rely on a sigmoidal or Hill-type dose–response model. A common form is E(D) = Emax × D^n / (D^n + ED50^n), where D is the dose, n is the Hill coefficient, and ED50 is the dose producing 50% of Emax. From this relationship, ED90 can be derived as ED90 = ED50 × 9^(1/n). In practice, ED90 is estimated by fitting a dose–response curve to experimental or clinical data and identifying the dose corresponding to a 90% response. Confidence intervals or credible intervals may accompany the estimate to reflect uncertainty.

Applications of ED90 include comparative potency assessment, dosing guideline development, and risk–benefit analysis in clinical pharmacology. It can inform decisions in areas such as anesthesia, analgesia, and targeted therapies where achieving a high level of effect with acceptable safety is important. ED90 values can vary by endpoint (e.g., pain relief, sedation), route of administration, population characteristics, and timing after dosing, so context is essential.

Limitations include dependence on the chosen endpoint, assay system, and population. Extrapolating ED90 beyond the studied conditions or using a single value across diverse groups can be misleading. ED90 is most informative when presented alongside the method used for estimation and associated uncertainty.