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Therapeutic Index:
Therapeutic Index:
A number, LD50/ED50, which is a measure of the approximate "safety factor" for a drug; a drug with a high index can presumably be administered with greater safety than one with a low index. The therapeutic index is ordinarily calculated from data obtained from experiments with animals. As in comparing ED50s from two different drugs, the comparison of the LD50 and ED50 (therapeutic index) is most meaningful when the dose-effect curves from which the ED50 and LD50 are inferred are parallel.
The therapeutic index is a measure of drug selectivity, and analogous index numbers are frequently computed to measure selectivity that does not involve lethal effects. For example, to measure the selectivity of a drug potentially useful in the treatment of epilepsy, the ED50 for producing ataxia in mice might be compared to the ED50 for abolishing electrically-induced convulsions in mice.
Cf. Median Effective Dose, Selectivity, Standardized Safety Margin, Clinical Therapeutic Index
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I
K
M
N
N
P
P
R
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Z
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