Psychiatric medicines are an important component of treating neurological and mental health disorders including depression, attention deficit disorder and schizophrenia. Dosing of psychotropic drugs can be challenging for the clinician because there is considerable variability in patient response to a drug. This variability is due to a number of reasons including the severity of disease being treated, diet, age and interactions with other medications. The finding were published in Psychiatry Journal “The Potential Utility of Pharmacogenetic Testing in Psychiatry” (2014).
Inherited genetic variants also affect the way that a drug is metabolized. Some patients experience side effects from a medicine while others may not get any therapeutic value at all. For example, up to 40 percent of patients prescribed the drug fluoxetine for depression, do not get any benefit from the medicine. The findings were published inCurrent Psychiatry Review “Jumping on the Train of Personalized Medicine: A Primer for Non- Geneticist Clinicians: Part 3. Clinical Applications in the Personalized Medicine Area” (May 2014).
Importance of Pharmacogenetic Testing for Psychiatric Medicines
Because of the variability in patient response and the potential for adverse reactions to a drug, clinicians have traditionally used a cautious trial and error method to select an appropriate medicine and determine optimum dosing. Although this approach minimizes side effects, it also delays the amelioration of symptoms. In an effort to relieve symptoms, physicians may use several medications. Combinations of drugs may result in over medication or cause side effects due to drug interactions. The findings were published in Dialogues in Clinical Neuroscience “Psychiatric pharmacogenomic testing in clinical practice” (Mar 2010).
Pharmacogenetic testing provides doctors with an important tool that helps determine which medicines are best suited to a patient’s unique medical condition. Variants of several genes are associated with differences in metabolism of psychiatric medications. Gene CYP2D6 is one of the most important phenotypes for psychiatric medicines. Amitriptyline, several antidepressants and several antipsychotics are metabolized by this gene. Other clinically important genes include CYP2C19, CYP2C9 and CYP1A2. Variations in these genes affect serum concentrations of medications which, in turn, influence drug effectiveness and the potential for adverse medication reactions. The findings were published in Dialogues in clinical neuroscience “Psychiatric pharmacogenomic testing in clinical practice” (Mar 2010).
So-called poor metabolizers assimilate medicines more slowly. The low metabolic capacity may cause toxicity or result in adverse events. Ultra-rapid metabolizers eliminate the drug too quickly and these patients are less likely to derive a therapeutic benefit. Intermediate metabolizers are at a higher risk of developing drug-drug interactions. The Food and Drug Administration has issued warning and dosage recommendations for more than 30 psychiatric medicines for patients with specific genetic variants. For example, citalopram require dosage modifications for ultra-rapid metabolizers. The findings were published in:
Dialogues in clinical neuroscience “Psychiatric pharmacogenomic testing in clinical practice” (Mar 2010; Table of Pharmacogenomic Biomarkers in Drug Labeling as reported by the FDA (Nov 2016); Current Psychiatry Review “Jumping on the Train of Personalized Medicine: A Primer for Non- Geneticist Clinicians: Part 3. Clinical Applications in the Personalized Medicine Area” (May 2014).
Rxight® Pharmacogenetic Testing
The FDA recommends pharmacogenetic testing before administering several psychotropic medications to minimize side effects and improve therapeutic outcomes. Rxight® pharmacogenetic testing examines a patient’s DNA to identify genetic variants on 60 alleles of 18 clinically significant genes that affect drug metabolism. The test covers approximately 200 prescription medicines including psychiatric medicines listed by the FDA.
Patients receive a personalized medication report. The information is interpreted by a pharmacist trained in pharmacogenetics. Pharmacists coordinate with a patient’s physician to help determine a medication and dose that has the potential for greater efficacy and lower risk of adverse effects. Adherence to a drug therapy program is of particular importance for patients with psychiatric disorders. When patients know that the potential for unpleasant side effects is reduced, they may become more confident in the safety of the treatment and gain better value from the medications. The findings were published in Pharmacotherapy “Pharmacogenomic Testing for Neuropsychiatric Drugs: Current Status of Drug Labeling, Guidelines for Using Genetic Information, and Test Options” (Feb 2014).