Effective dose

In pharmacology an effective dose is the amount of drug that produces a therapeutic response in 50% of the people taking it. In radiation protection effective dose is an estimate of the stochastic effect that a non-uniform radiation dose has on a human.

Radiation
Effective dose is used in radiation protection, to compare the stochastic risk of a non-uniform exposure of ionizing radiation, with the risks caused by a uniform exposure of the whole body. The stochastic risks are carcinogenesis and hereditary effects. It is not intended as a measure for acute or threshold effects of radiation exposure such as erythema, radiation sickness or death.

Effective dose equivalent is used to compare radiation doses on different body parts on an equivalent basis because radiation does not affect different parts in the same way. The effective dose (H) to an individual is found by calculating a weighted average of the equivalent dose (E) to different body tissues, with the weighting factors (W) designed to reflect the different radiosensitivities of the tissues:

H = ∑i Ei Wi

The unit for effective dose is the sievert (Sv).

The International Commission on Radiological Protection provide guidance on the risk caused by radiation.

Pharmacology
In pharmacology, effective dose is the minimal dose that produces the desired effect of a drug. The effective dose is often determined based on analysing the dose-response relationship specific to the drug. The dosage that produces a desired effect in half the test population is referred to as the ED-50, for "Effective dose, 50%".