Fig. 3.

Hypothetical relationship between the inherent toxicity of drugs and the variability of the response among hosts (e.g. test animals, humans). The dose is not a consideration in this treatment, adapted from Zimmerman.^9,10) At toxic doses, the most readily understood compounds are those with high toxicity in all animal species. Variation among species introduces more uncertainty in extrapolation to humans. Predictions can be made if the issue is metabolism but idiosyncratic problems are very difficult to understand with animal models.