Drug response varies widely among patients, depending on each patient’s intrinsic and extrinsic factors. A starting point of personalized pharmacotherapy is to integrate information about all of those factors into knowledge. Drug response can be divided into 4 processes; drug administration, pharmacokinetic (PK) process, pharmacodynamic (PD) process, and clinical safety/efficacy. Variability in drug response is thought to arise from variability in each process caused by intrinsic and extrinsic factors. A fundamental intrinsic factor is genomic influence, which influences all processes involved in drug response. Due to the limitation of methodology and difficulties in conducting clinical research, PK data was the majority of information in the past. However, development of methodological tools such as imaging and newly developed biomarkers made it possible to generate a myriad of genomic information related to PD and clinical response. Furthermore, in the aspect of genomic analysis tools, more efficient and comprehensive approaches are available which may accelerate the accumulation of genomic information in the future. While an individual’s genotype does not change, the process of genome transcription/translation and effects of protein on the human body may be modified by intrinsic and extrinsic factors. In this point, epigenetics, transcriptomics, proteomics, metabolomics, disease genomics, microbiomics and integrated information of these fields would become pivotal in addition to pharmacogenomics. Moreover, algorithms for optimized drug therapy in individual patients should be developed and verified, based on databases of aforementioned information and patient-specific extrinsic factors including demographic and physiological information and co-medications.