The human body is a miraculous thing that perpetuates its own survival by constantly repairing itself. To do so, the body processes everything it takes in by using what is beneficial and getting rid of what is not. Enzymes make this possible. Enzymes are little catalysts that cause chemical reactions in the body when they find the right substrate. We ingest substrates all the time when we breathe, eat, drink, sunbathe, take vitamins, take drugs, etc. Laboratory analysis of the genes that determine enzyme production is called pharmacogenetic testing.
What does pharmacogenetic testing tell us?
A special family of enzymes called cytochrome P450 (CYP) is primarily responsible for metabolizing drugs so that they can be used by the body. There are over 50 CYP enzymes, six of which are responsible for the metabolism of 90 percent of drugs and medications. Genetic variations in these enzymes determine how drugs are broken down, transported, absorbed and excreted, which is why the same drug affects everyone differently.
Some people do not produce any such enzymes at all and others produce a lot. Of those who do, some produce them rapidly and others slowly. For example, some people do not make enzymes in response to a certain antidepressant. Such a person will not experience any improvement from the medication, but might experience only the side effects. Conversely, others may metabolize the same medication so rapidly that it never has a chance to take effect.
Medications interact with various systems in the body to produce a therapeutic effect. Analyses of the genes responsible for the structure and function of the targeted body system help predict who will benefit from treatment. Rather than giving everyone with a certain diagnosis the same dose of the same medication, medical therapy can be customized based on genetic information.
Psychopharmacogenetic testing (PGT) is the laboratory analysis of a person’s many different genes that determine enzyme production in response to psychotropic medications. When reporting PGT results, numbers and letters refer to the various gene families, subtypes and individual genes. To date, PGT has mainly been used to determine which drugs will be most effective for individual patients.
PGT may soon be able to also determine what dosage individual patients may require. Lithium is the drug of choice used to treat bipolar disorder, but it has a narrow therapeutic range. Too much can be toxic and too little may not improve symptoms. A new study explored the use of PGT in determining treatment response, an important factor for determining safe and effective therapeutic lithium levels. Genetic variances were described that may give doctors information about how patients will respond to lithium before it is started.
Another new study analyzed the genomes of 263 adults with schizophrenia and compared the results with the patients’ medication dosages. The researchers did isolate a gene that was significantly correlated to medication dosages. They suggested more research be done to describe how it can be applied to tailor medications to individual patients.
PGT is now available at select treatment centers across the country, including Sovereign Health.
Dana Connolly, Ph.D., is a senior staff writer for the Sovereign Health Group, where she translates current research into practical information. She earned her Ph.D. in research and theory development from New York University and has decades of experience in clinical care, medical research and health education. The Sovereign Health Group is a health information resource and Dr. Connolly helps to ensure excellence in our model. For more information and other inquiries about this article, contact the author at firstname.lastname@example.org.