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Can a Gene Test Help Pick the Right Meds?



What if, using a simple cheek swab, your doctor could pinpoint the right ADHD medication and the right dose for you on the first try? 

The possibility is not too far away. The emerging field of pharmacogenomics  holds the possibility of using the information from your unique set of genes to select medications and doses tailored to work best for your body. For most people, finding the right medication at the right dose for them, or their children, is frequently a time-consuming and frustrating process. Often, people need to change medications or doses more than once, which can lead some people to discontinue medication management entirely because “it didn’t seem to be working.”

The right medicine, according to your genes

Researchers in the 1950s began exploring why some families and ethnic groups had different and unexpected responses to medications then in use. This field of research was dubbed “pharmacogenetics,” the study of how variation in a single gene influences the response to a single drug. It was a ground-breaking understanding in medicinea certain gene in your body could determine whether you could take and benefit from a medication.

In recent years, the field of study has changed and expanded in its approach, studying medicine for brain-based health conditions, not just body-based conditions. With this has come the current study of “pharmacogenomics”–specifically developing and choosing medications based on how all one’s genes and gene products can influence responses to drugs. Pharmacogenomics has the potential to improve mental health treatment, including medication management for ADHD. Researchers expect it will further the practice of personalizing ADHD treatment.

Already, there is pharmacogenomics research examining the wide range of responses to stimulant medications for ADHD, noting, “variability exists in clinical outcome, which may reflect underlying genetic influences.”

Pharmacogenomics to improve ADHD treatment

Researchers are looking at how to use pharmacogenomics to create new medications and therapies for ADHD treatments. Knowing which genes are involved in ADHD could allow researchers and doctors to predict how well a new medication or a new treatment approach works as treatment for a person or a group of people with similar genetic characteristics. There are currently ongoing studies to understand more about how genes can be used to predict responses to treatment, as well as to drive new treatments based on existing genetic information.

Another benefit is doctors will be better able to prescribe medications and understand why a medication did not work for a person or why that person stopped taking a medication that seemed effective, again leading to a better targeted treatment plan for the individual person.

“If [these studies are] successful, personalized ADHD therapy will move quickly from the ‘promise’ to the ‘practical’ phase,” say Mark A. Stein, PhD, and James J. McGough, MD, who reviewed multiple studies for The Pharmacogenomic Era: Promise for Personalizing ADHD Therapy.

“Pharmacotherapy has an essential role in the treatment of ADHD,” write Estela Maria Bruxel, PhD, and colleagues. “Such information could improve treatment by shifting from trial-and-error approach to a pharmacological regimen that takes into account the individual variability. Given the small effect of genetic variants studied so far, it is an open question whether, how, or when results from ADHD pharmacogenetics studies will be useful in clinical management.”

Personalizing your medications

Pharmacogenomics—identifying medications based on your genes and how they work—intends to personalize medicine and prevent medications’ side effects or losing effectiveness.

“This relatively new field allows us to combine pharmacology and genomics to develop effective and safe medication dosages which are specific to an individual’s DNA makeup,” writes Soram Khalsa, MD, for Pharmacogenetics: What It Is and Why You Need to Know. “In my practice, it is the first practical application of our cracking the human genome code that we have available for day-to-day use with patients.”

Dr. Khalsa points out that how a person’s body metabolizes a medication affects how well that medication will work for the person. It also explains why one person will need a different dosagehigher or lower than her peers—to achieve the same response. It also explains why some people will experience a side effect to a medication that others will not have. Doctors can now order genetic tests to help guide them in selecting medications, including ones for some mental health conditions, for their patients.

“The laboratories give us a beautiful spreadsheet-like chart that shows us which drugs your body is programmed to be able to break down in the normal fashion and which drugs you will not be able to break down in the normal fashion,” Dr. Khalsa says. “It’s probably been your experience that one of your friends or your family members has gotten a drug that didn’t agree with them or gave them significant side effects. One of the reasons for these problems is that the person does not have the genes that create the biochemical pathways to break down the medication.”

When it comes to ADHD, the potential is clear: By reviewing a patient’s genetic information, a doctor could better decide which medication class, stimulant, non-stimulant, or atypical, and even which specific medication would work best for that patient. Rather than a protracted medication trial with multiple types or doses, the doctor can select the right medication and pinpoint the right dose relatively quickly.

It also means, as  Dr. Khalsa points out, fewer side effects from medication, less discomfort, and a greater likelihood that a person will remain with the decided upon treatment plan.

The future of medication management for ADHD

At the present, not all medications for ADHD have been studied or reviewed from a pharmacogenomics standpoint. As new medications are developed, or older ones are re-elevated, such information will become available.

Researchers, though, are calling on doctors and medical professionals to become familiar with pharmacogenomics now, and start talking with their patients about the current and future benefits of medical genetic testing.

“[P]hysicians should become familiar with the terms used in medical genetics and pharmacogenomics and begin to understand genetic contributions to the outcomes of drug therapy,” write Joseph P. Kitzmiller, MD, PhD, and colleagues in Pharmacogenomic testing: Relevance in medical practice.  “Understanding the consequences of … variants in a given population can be tremendously helpful when advising our patients about anticipating potential problems when taking specific medications. This exchange of information alone may go a long way in improving therapy.”

Talk with your prescriber about a new approach

If you or your child currently takes medication as part of an ADHD treatment, and you are not seeing the results you would like, you may want to talk with your prescriber about the possible benefits of a genetic test to help determine a good medication fit.

It is not currently part of standard clinical practice to complete a genetic test as part of prescribing medication for ADHD nor for most brain-based health conditions. There are costs involved that may out-weigh any potential benefit that you may need to consider. Your doctor can best guide you in determining if a genetic test would be helpful to inform your treatment plan or if it is best to wait on such testing until a time that it could be helpful for you.

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This article appeared in ADHD Weekly on August 24, 2017.
     


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