The future (or lack of future) of personalized prescription in psychiatry

Rapid technological advances in genetics have created conceptual chaos regarding the genetics of drug response. Terms for differing concepts are used interchangeably: pharmacogenetics with pharmacogenomics, personalized medicine with personalized prescription. Biomarker has many definitions. The author prefers the concept of personalized prescription and uses it with implications beyond pharmacogenetics by considering all scientific information valid for prescribing medication. Genetics may not be crucial for all drugs. In this comprehensive view, clinicians must consider genetic, environmental and personal variables when prescribing medication and incorporate some basic pharmacological principles: (1) safety and efficacy, (2) pharmacokinetics and pharmacodynamics, (3) therapeutic window and prescriber's role, and (4) idiosyncratic and dose-related adverse drug reactions. Personalized prescription in the clinical environment can be expressed in two main ways: as personalized selection of the drug and as personalized dosing. The future, or lack of future, of personalized drug selection and of personalized dosing in psychiatry is reviewed. Currently, the author thinks that, in psychiatry, pharmacogenetic tests have some potential in two areas: (1) excluding some drugs for some unusual patients (HLA-B*1502 genotyping in Asians for carbamazepine), and (2) using pharmacokinetic genes for personalizing dosing in narrow therapeutic window drugs. In the short term, there is dubious potential for other pharmacogenetic tests and no potential for pharmacogenetic testing to ascertain the best drug for each patient. Personalized dosing has immediate application if one understands it as the use of our current scientific knowledge of genetic, environmental and personal variables to determine dosing; its sole requirement is well-trained psychiatrists.