An effective dose in pharmacology is the amount of drug that produces a therapeutic response in 50% of the people taking it, sometimes also called ED-50. In radiation protection it is an estimate of the stochastic effect that a non-uniform radiation dose has on a human.It is measure of potency of the drug.

[edit] Pharmacology

In pharmacology, effective dose is the median 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%".

[edit] Radiation

In Radiology, effective dose is defined in the same way as it has been in pharmacology above, and a figure that could be used in calculating a certain safety factor, the 'effective dose' would be the absorbed dose (whole body equivalent) required to achieve an adequate (diagnostic) image.

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 (Now replaced by Effective Dose) 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 (E) to an individual is found by calculating a weighted average of the equivalent dose (H) to different body tissues, with the weighting factors (W) designed to reflect the different radiosensitivities of the tissues:

E = ∑_i H_i W_i

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

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

[edit] References

• ICRP. ICRP Publication 60: 1990 Recommendations of the International Commission on Radiological Protection. Elsevier Science Pub Co (April 1, 1991). ISBN 0-08-041144-4.

[edit] See also

• List of abbreviations used in medical prescriptions
• Certain safety factor
• LD50