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Why it's done
By Mayo Clinic staffMedications for depression are usually prescribed based on symptoms and medical history. For some people, the first antidepressant tried relieves depression symptoms and has tolerable side effects. For many others, however, finding the right medication takes trial and error. For some people, it can take several months or longer to find the right antidepressant.
Genotyping tests, such as cytochrome P450 tests, may speed up the identification of medications that are more likely to be better processed by your body. Ideally, better processing would lead to fewer side effects and improved effectiveness. Cytochrome P450 tests are generally used only when initial antidepressant treatments aren't successful.
Genotyping tests are also used in other areas of medicine. The 2D6 test can help determine whether certain cancer medications, such as tamoxifen for breast cancer, are likely to be effective. The 2C9 test can help determine appropriate dosing of the blood thinner warfarin (Coumadin) to reduce the risks of adverse effects.
- Mrazek DA. Psychiatric pharmacogenomic testing in clinical practice. Dialogues in Clinical Neuroscience. 2010;12:69.
- Wand L, et al. Genomics and drug response. The New England Journal of Medicine. 2011;364:1144.
- Goetz MP. Update on CYP2D6 and its impact on tamoxifen therapy. Clinical Advances in Hematology & Oncology. 2010;8:536.
- McAlpine DE, et al. Effect of cytochrome P450 enzyme polymorphisms on pharmacokinetics of venlafaxine. Therapeutic Drug Monitoring. 2011;33:14.
- Fleeman N, et al. Cytochrome P450 testing for prescribing antipsychotics in adults with schizophrenia: Systemic review and meta-analysis. The Pharmacogenomics Journal. 2011;11:1.
- Genetic testing — CYP450 genotyping to predict response to SSRIs used to treat non-psychotic depression in adults: EGAPP recommendation. Centers for Disease Control and Prevention. http://www.cdc.gov/genomics/gtesting/EGAPP/recommend/CYP450.htm. Accessed Aug. 29, 2012.
- Steimer W. Pharmacogenetics and psychoactive drug therapy: Ready for the patient? Therapeutic Drug Monitoring. 2010;32:381.
- Mrazek DA, et al. Facilitating clinical implementation of pharmacogenomics. JAMA. 2011:306:304.
- Kung S (expert opinion). Mayo Clinic Rochester, Minn. Aug. 15, 2012.
- Coumadin (prescribing information). Princeton, N.J.: Bristol-Myers Squibb Company; 2011. http://packageinserts.bms.com/pi/pi_coumadin.pdf. Accessed Aug. 21, 2012.
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