Many psychiatric patients experience pharmaceutical intolerances, and some of them do not derive optimal efficacy from their pharmacotherapies. Clinical problems such as these may result in prolonged dysfunction, adverse consequences, and repeated changes in medication treatment regimens. Pharmacogenomics is a laboratory method that aids individualized medication selection by predicting drug efficacy and adverse effect profiles. It is a technique that involves the testing of patients' genetic makeup to improve medicinal response and tolerance. Pharmacogenomics aims to clarify pharmacokinetics and pharmacodynamics in addition to focusing on hepatic cytochrome enzyme metabolism. Ultimately, it facilitates optimal selection and adjustment of medications to enhance clinical outcomes. Pharmacogenomics is most useful in cases in which routinely prescribed pharmacotherapies are either suboptimally effective or have unacceptable adverse effects. Once there has been a failure of a therapeutic drug treatment, rather than "blindly" selecting an alternative medicine, pharmacogenomic test results can provide guidance for the selection of the most appropriate drug and its dose. The intent is to yield a greater likelihood of patient success in following a therapeutic intervention.