Pharmacogenomics: Towards A New ERA Of Personalized Medicine In Psychiatry?

Abstract

BackgroundPharmacogenomics (PGx) is a field of study and clinical tool that assesses how genetic variability influences drug response and tolerability.CYP450 enzymes are responsible for metabolizing most psychiatric medications. Based on their genetic make-up, an individual may be classified as an extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), ultra-rapid metabolizer (UM).Given the increasing evidence for genetic influences on treatment response, we deemed it important to study physicians' opinions and patients' outcome following pharmacogenetic testing for CYP2D6, CYP2C19 among other genes. MethodsInitially, only CYP2D6 and CYP2C19 genes were genotyped and treatment recommendations for antidepressant and antipsychotic medications were provided to physicians. This initiative expanded to include additional CYP enzyme genotyping such as CYP2C9, CYP3A4, CYP2B6, CYP1A2 and serotonin-related genes SLC6A4 and HTR2A. Six to eight weeks after physicians were provided with their patients’ genetic information, we sent our Pharmacogenetics in Psychiatry Follow-up Questionnaire (PIP-FQ) survey to psychiatrists and primary care physicians. ResultsFrom the 620 physicians who were sent PIP-FQ surveys for the PGx study, 383 returned the survey for a response rate of 61.8%. Of all respondents, 58.1% were female, 43.7% were over 50 years old, and 59.7% were general practitioners while 32.7% were psychiatrists. From all respondents, 90.6% indicated that they understood the PGx report they received, 79.1% were satisfied with it, and 75.7% would agree that PGx testing will become standard for psychotropic pharmacotherapy. Of those given treatment recommendations by the PGx report, 57.1% found the report helpful for further treatment decisions and 77.5% said they would remain interested in referring additional patients to the study. Remarkably, when physicians took treatment recommendations into consideration, 120 of 211 (56.9%) patients were reported to benefit from the recommendation compared to baseline, with only two patients worsening following the change (p < 0.01). ConclusionsOur results show that physicians feel favourably towards PGx testing for psychiatric medications and the information provided by the PGx report. Patients saw beneficial changes to both their symptoms and side effects, and were satisfied by outcomes resulting from the genetic tests. Although our sample size of 383 physicians is among the largest for such a survey, about 38% have not returned the questionnaire. While this represents a good response rate, the possibility of response bias may overemphasize positive opinions. However, because our sample of physicians provided uncompensated feedback to questions at no extra costs, it is arguable that the effects of these limitations are small.