Genetic Influence on Medication Response

Pharmacogenetic testing aims to genetically guide prescriptions to improve patient response and decrease side effects. We are living at an exciting time in science and pharmacogenetic testing is another tool that can guide a more precise treatment plan. Factors such as the environment and lifestyle choices (nutrition, exercise, meditation, etc) are always taken into consideration when arriving at the best treatment plan for each individual.

On my recent podcast I had the honor of interviewing Daniel Mueller M.D., Ph.D who is an associate professor at the Department of Psychiatry at the University of Toronto and is the Head of the Pharmacogenetics Research Clinic at Center for Addiction and Mental Health and is a clinical psychiatrist at the Mood and Anxiety Program at CAMH.

Dr. Mueller and I discussed the importance of genetic factors, specifically the genes encoding for CYP450 liver enzymes. CYP450 enzymes are a group of mixed function monooxygenases that are responsible for metabolizing almost 50% of all marketed drugs (*Gibbs et al.,2005).

Polymorphisms (genetic variation) in the CYP450 genes yield enzymes with different pharmacodynamics (the study of how the drug affects the organism) and pharmokinetic (the study of how an organism affects a drug) properties. An individual may be classified as an extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), ultra-rapid metabolizer (UM) (*Gibbs et al., 2005). Dr. Mueller discussed the benefits of using pharmacogenetic testing for clinicians to identify outliers who are non-EM status and who carry higher risks for non-response, adverse events and side effects.

*Gibbs, C., Fisher, P., Hernandez, J., Mrazek, D., O’Kane, D., Snyder, K., 2005. Cytochrome P450 Enzyme Genotyping: Optimizing Patient Care Through Pharmacogenetics, In: Services, M.R. (Ed.), pp. 1-10.

Dr. Mueller and I discussed that at present the use of pharmacogenetic testing is not mainstream (yet?) due to cost and the need for continued research. If you have a history of poor response to medication or intolerable side effects ask your doctor if a consideration for a pharmacogenetic test would be beneficial to maximize your treatment and wellness plan. It is important to remember that pharmacogenetic testing is a tool that is utilized in combination with your doctor’s expertise and that there are multiple factors that play a role in your health and wellbeing.

Thank you Dr. Mueller for your contributions to science and psychiatry.

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