Salma Malik, Charles F Caley, Muhammad Waqar Azeem.
Psychopharmacogenomics: a new tool for the prescribing physician.
J Pak Psych Soc Jan ;11(2):12-5.

The evolution of personalized medicine has begun, and personalized psychiatry is following the approach of personalized medicine. The US Food and Drug Administration (FDA) reports that there are currently over 100 prescription medications that have pharmacogenomic information in their product labels and approximately 30% of these are psychotropic medications. For these psychotropics, the pharmacogenomic information included within the label addresses genotypes of either CYP2D6 or CYP2C19. This makes our understanding of cytochrome P450 enzyme (CYP450) pharmacogenomics especially important. In addition, a high percentage of psychotropic medications are metabolized by these enzymes. Enzymes that are most relevant to the metabolism of psychotropics include CYP450 1A2, 2B6, 2C9, 2C19, 2D6, and 3A4. The fields of pharmacogenomics and pharmacogenetics have experienced tremendous development. Polymorphisms in the genes which code for the production of CYP450 enzymes can alter the rate at which affected enzymes can metabolize medications (also referred to as substrates). For each enzyme, a patient may be characterized as being an: extensive (normal) metabolizer, intermediate metabolizer, poor metabolizer, or ultra-rapid metabolizer. Extremes in metabolic rates resulting from gene polymorphisms may contribute to either poor tolerability (poor metabolizers), or to poor efficacy (ultra-rapid metabolizers) when using psychotropics that are dosed in anempirical manner. The capacity to genotype a patient`s CYP450 enzymes is currently available. Therefore knowing the patient`s inherited metabolizer status can be helpful in selecting psychotropic medications that avoid metabolism through a polymorphic pathway, or to adjust a dosing strategy in an effort to avoid poor treatment outcomes when the patient is treated with a medication that is being metabolized through a polymorphic pathway. This review will focus on the metabolism of psychotropics and important aspects of understanding the genomics of the cytochrome P450 enzymes. This review will also discuss a case scenario which illustrates a process that physicians can use when applying genomic laboratory data to patient care.

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