An individual’s response to medicine is written in our genetic makeup, which is why there is not at one-size-fits-all medication for mental disorders such as bipolar disorder, depression, ADHD, schizophrenia, among other mental health disorders. Genetic testing can help pinpoint which medications work best for individual patients.
When a psychiatrist can see the results of your report, he or she can understand why a person’s genetic makeup affects how certain drugs may react and personalize treatment choices for that individual. For example, with ADHD, the tests will show genes that may affect a patient’s response to certain antidepressant or antipsychotic medications. The report can predict the influence of genes on the drug as well as metabolism.
Our bodies contain numerous cytochrome P450 (officially abbreviated at CYP) enzymes that process medications. CYP is a large, diverse group of enzymes that can help predict drug metabolism and bioactivation. CYPs account for about 75% of the total metabolism of a drug.
The CYP2D6 genotype, for example, indicates that blood levels may be increased for a particular drug. Genotype is simply the genetic makeup of a cell or organism with specific reference to a specific characteristic. It tells the doctor how your body will metabolize a certain drug. The report indicates four categories: 1) poor metabolizer – little or no CYP2D6 function; 2) extensive metabolizer – normal CYP2D6 functioning; 3) intermediate – somewhere between poor and extensive; and 4) ultra-metabolizer – individuals with multiple CYP2D6 copies, or a duplication of the gene.
For an ADHD patient, known inhibitors by the CYP2D6 enzyme include Adderall, Vyvanse, Dexedrine, and Strattera. The report gives psychiatrists three categories of medications to prescribe: 1) those to use as directed; 2) those to use with caution; and 3) those to use with caution with more frequent monitoring. This list is then readily available to the doctor to utilize to prescribe medications they think will work best, and which ones to avoid for a particular patient.
For an ultra-metabolizer, for example, an antidepressant to use as directed is Wellbutrin. One to use with caution is Lexapro. And one to use with caution with frequent monitoring is Cymbalta. It does not mean that Cymbalta cannot be prescribed, but it gives the doctor more information on how the individual’s body will respond and that it should be monitored frequently.
Along with genotype, the report also includes phenotype information. Phenotypes result from the expression of the individual’s genes as well as environmental factors and the interaction between the two. For an ultra-metabolizer, where the CYP2D6 is duplicated, a higher dosage of certain medications may be needed, because increased metabolism cannot be accurately anticipated and frequent monitoring in needed.
The induction or inhibition of commonly prescribed mental health drugs may vary from patient to patient as well as the potential for drug interactions, and a genetic test report can help the doctor predict this for an individual patient and choose the most appropriate medications. A doctor can use genetic testing reports for individual patients as a guide tailored to the specific circumstances of each patient with genotype and phenotype information. Ultimately, it is the doctor’ choice to make medication and treatment decisions, but genetic testing is a useful tool to use on the basis of each patient’s results.