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SlothMcCarty (talk | contribs) stub--adapted from Therapeutic index |
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<math>\mbox{Protective index} = \frac{\mathrm{TD}_{50}}{\mathrm{ED}_{50}}</math>
The protective index is similar to the [[therapeutic index]], but concerns toxicity ([[TD50|TD<sub>50</sub>]]) rather than lethality ([[LD50|LD<sub>50</sub>]]); thus, the protective index is a smaller ratio. Toxicity can take many forms, as drugs typically have multiple side effects of varying severity, so a specific criterion of toxicity must be specified for the protective index to be meaningful. Ideally a choice is made such that the harm caused by the toxicity just outweighs the benefit of the drug's effect. Thus, the protective index is a more accurate measure of the benefit-to-risk ratio than the therapeutic index, but is less objectively defined. Nevertheless, the therapeutic index can be viewed as an [[upper bound]] to the protective index for a given substance.
{{Pharmacology}}
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