Median Doses: LD50, ED50 and TD50

Important definitions


important definitins - ec50 ld50 td50


ED50:  Median effective dose

The dose required to achieve 50% of the desired response in 50% of the population


TD50:  Median Toxic dose of 50% for 50%:

The dose required to get 50% of the population reporting this specific toxic effect


LD50:  Median lethal dose.

The dose required to achieve 50% mortality from toxicity


EC50:  Half maximum effective concentration

The concentration of a drug at which 50%  of its maximum response is observed


LC50:  Half lethal concentration

The concentration of a drug at which 50%  mortality from toxicity is observed


For this sort of really basic stuff, no matter where you look you will find essentially the same information.

I used chapters from “Goodman & Gilman’s The Pharmacological Basis of Therapeutics” 11th ed by Brunton et al, and “Basic & Clinical Pharmacology” 11th ed. By Katzung et al.


I also perused Peck and Hill “Pharmacology for Anaesthesia and Intensive care” as well as the notoriously error-prone “Handbook of Pharmacology and Physiology in Anaesthetic Practice” by Stoelting and Hillier. Neither covered this subject in a depth I found satisfying.


Goodman and Gilman’s remains a canonical text.

Search form

Submit Correction

Last updated:

Tuesday, June 30, 2015 – 01:34