For the quantitative assessment of therapeutic/pharmacologic effects and adverse/toxic effects of drugs which interact with several specific receptors, we developed an integrated pharmacokinetic analysis system by considering a receptor occupancy theory and a ternary complex model. The developed system has made it possible to predict the optimal dosage for the investigation of drugs using pre-clinical and clinical data (phase I study) under development, and to assess quantitatively the intensity of adverse/toxic effects of drugs which are not observed in the stage of clinical study. As for commercially available drugs, the developed system may be useful for planning the rational drug dosage regimen to obtain desired therapeutic effects with minimum adverse/toxic effects. Our new methodology for the rational dosage regimen of a new drug will be established based on the results of this study.