The choice of effective psychotropic drugs for patients with psychiatric conditions is often difficult. It is hard to predict the clinical effect of the drug, to determine why a drug has a positive clinical effect on one patient but not on the other who has the same condition. The article explains how pharmacogenetic testing could help optimize psychopharmaco-therapy, reduce the direct and indirect costs of mental illness, improve the quality of life of the patients with psychiatric conditions. Evaluating the disability adjusted life years, the burden of mental illness and the most common psychiatric disorders in the United States and Europe is also shown. The article also reviews the effect of cytochrome CYP450 system on psychotropic drug metabolism, the importance of genetic polymorphisms of the different cytochrome families and their possible effect on drug dosage. We review the four phenotypes of the drug metabolising enzymes, discuss their importance in choosing the right drug and drug dosage for each individual patient and the possible adverse effects the drug might or might not have on each patient depending on his metabolism type. The mutations of psycho-tropic drug target receptor (COMT, MAOA, CRH, DDR, 5HT) genes, the HPA axis, signal transduction pathways and neurotropic factors that could alter the efiect of the drug in an organism are also reviewed as well as the most used psychotropic drugs, their mechanisms of action, therapeutic indications, most important adverse effects and the genetic polymorphisms that could change the desired effect of the drug. We also demonstrate how pharma-cogenomic testing could be used in clinical practice using an example study carried out in Chicago, that reflects on the problems of primary drug choice for individuals in modern psychiatry, explained how it could help the doctor and the patient alike. We also reviewed the modern laboratory tests used to identify genetic mutations and polymorphisms.
Keywords: pharmacogenomics, pharmacogenetics, polymorphism, CYP450, psychotropic drugs.