Method for determining the dose of at least one active agent based on a genetic analysis. The method comprises analyzing specific genes for their nucleotide sequence or their expression levels of gene-specific proteins and/or RNA molecules. The gene-specific data is assigned one or more relevant physiological functions of the human or animal body, in particular those which have an influence on the metabolism, absorption, excretion or distribution of the active agent in the body. The gene-specific data and the assigned physiological functions are then integrated into a physiology-based pharmacokinetic model (PBPK model). The PBPK model integrates pharmacokinetic data relating to one or more active agents. The PBPK model may also receive and evaluate patient-specific data directly inputted and combined with data from a knowledge database comprising known values of pharmacokinetic parameters. The PBPK's integration of these data provide a calculation of the individual dose of the active agent.