In drug discovery and development, the kinetic study of active metabolites plays an important role, helping to define the time course of the drug in the body and its activity or toxicity. After a pharmacokinetics assessment of a drug and its metabolite or a prodrug and its parent-drug, several parameters can be calculated. In some cases, achieving the objective of the study does not require all possible parameters to be calculated. When parameters are calculated, it is essential that their denotations are widely accepted and used. However, some parameters undergo a certain variability of denotation, which may confuse some readers. Thus, this review summarizes the current published data for experimental pharmacokinetic parameters of metabolites and the calculations involved in simple metabolite pharmacokinetic studies. It also evaluates the most common pharmacokinetic parameters in the literature and suggests metabolite parameters that could be determined to help advance metabolite kinetic models.