**2. Case example: Toxicokinetics and testicular toxicity**

This case example (described below) will highlight 1) preferential distribution of parent and metabolites to tissue, 2) a predominant metabolite that is different in the tissue versus plasma, and 3) accumulation of parent and metabolite that occurs in tissue and not in plasma. Furthermore, the case example will highlight that focusing on tissue burden of the drug and its metabolites (and not plasma concentrations) may actually ensure that a backup does not produce the same toxicity.
