“Gene-testing said that my daughter cannot take stimulants for her ADHD.” A reader sent that to me in 2015. As a result, the girl was taking only Strattera, at a “maxed-out dose,” and not experiencing a significant decrease in ADHD symptoms. Something didn’t sound right. What was this “gene-testing”?
From her mother’s report, the seven-year-old girl was lost in the fog of ADHD. Unable to follow the teacher’s communication, she couldn’t even play games reliably with the other school children. As a result, the mother was looking into alternative education.
She’d asked for my opinion, but she didn’t like it. She did not want to hear she might be misunderstanding the test results. After all, I’m not a physician. Unfortunately, she didn’t worry about her physician misunderstanding the test results.
I worried for that child—and all the people whose physicians were getting it wrong. That’s why I recruited my husband. He has a doctorate in molecular biology and has taught medical students. He has worked for many years in genomics. And he has ADHD. Boom.
Silly me. I optimistically thought we could write one post to clarify this subject. Instead, it took seven! That’s because there are so many scientific terms. It was impossible to explain genetic testing without defining these terms — and offering examples. Pharmacodynamics. Pharmacokinetics. Genotyping. Enzymes. Oh my!
All that is to say, welcome to Part 3 in a series examining the utility of gene-testing to help choose ADHD medications. It is the first online collaboration between my husband (Dr. Goat) and me (Gina Pera), and we are thrilled by the enthusiastic response! In this post, we explain what the term gene-testing — also called genotyping — means.
Please Know: There Are Limits to These Tests
Genotyping tests are only one piece of a complicated puzzle. Please do not assume that your test results provide the sole factor in guiding your or your loved one’s medication choices. That is far from the truth. In this series, we explain exactly why—from several angles.
Gene-Testing: Defining the Term
By Dr. Goat
Several companies are making consumer-level tests available. Their purpose? Revealing the kind of drug-response genes the consumer might have. Some of these tests require a doctor’s prescription. Others offer workarounds, in case your own prescribing physician is unfamiliar with the testing. Costs vary.
The point of this blog series: to examine how these tests, in general, might prove useful—or not.
Though far from perfect, these tests can now provide valuable insights into what drugs, at what dosage, might be best for treating your or your loved one’s ADHD— and which drugs might pose complications.
This post establishes a foundation for understanding these genetic influences. Subsequent posts will examine one particular test in the context of my particular results (Gina’s, too!). We’ll also cover general interpretations of how one’s test results might influence treatment. The rest is up to you and your physician.
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[Update: We used the Harmonyx testing, made available via drugstore pharmacists. It was later restricted by the FDA. Other labs offer similar testing by prescription from MD—for example, Genesight and Genomind. These blog posts are pertinent to any type of gene-testing that claims to inform ADHD drug-response.]
You won’t come away from this series of posts knowing everything about genes and drug-response. But you will gain a good general understanding to benefit your, your patient’s, or your loved one’s ongoing healthcare treatment. Best of all, you will be better able to participate in treatment decisions.
Hey Genes, What’s Your Type?
We refer to these genetic tests as performing genotyping, so they’re called genotype tests.
First, let’s examine the term genotyping. Your genotype is your particular genetic makeup. So, when we talk about genotyping an individual, we simply mean performing tests that identify what kinds of genes are present in that person’s cells.
Of course, all humans have the same basic genes, but each particular gene comes in a particular “variant.” (Technically, it’s an allele. But because I’m writing for a lay audience, not a scientific one, let’s keep it simple).
Genotyping is one component “personalized medicine” trend. That is, where health assessments and treatments keep the individual in mind, instead of what has been shown to work in large groups of people.
Some gene variants are associated with different functional consequences. What is a functional consequence? Consider the following analogy.
Most adults drive a variant of four-wheeled vehicles. Some drive a truck powered by a robust engine that makes it possible to haul big loads—though at the cost of low gas mileage. Others drive a car with a weaker engine that provides the owner with excellent gas mileage—though at the cost of power.
The same is true of genes: one variant of a gene is associated with certain properties; other forms of the gene have other properties.
This is what genotyping does: it tells you whether your vehicle (that is, a particular gene) is a truck, a fast car, a gas-efficient car or, let’s face it, a clunker. Genotyping tests can do it for one gene or many genes.
Genes, Meet Medication; Medication, Meet Genes
There are two main aspects of pharmacogenomics—the study of understanding genetic influences (genomics) when it comes to medication (pharmaco):
1. Pharmacokinetics: “What the body does to the medication”
Many genes are known to affect how the body metabolizes a drug—in other words, how the body processes and ultimately discards the medication. For example, some genes affect the rate at which the body removes a drug from the blood.
Pharmacokinetics seeks to tell us about what happens to the drug, beginning when it enters the body and ending when it is completely eliminated from the body.
2. Pharmacodynamics: “What the medication does to the body”
Other genes influence the mechanism of how drugs affect cell function. Pharmacodynamics seeks to tell us about the mechanisms of drug action—how it affects the body—and the relationship between drug concentration and effect. In short, it tells us how the drug works.
All drugs have specific mechanisms of desirable action as well as various adverse effects that are caused by pharmacological interactions in the body.
Depending on your genetic variants, your particular response to a medication may be weaker or stronger than another person’s.
Keeping with the vehicle analogy, you may have to stomp harder on the accelerator of a car with low horsepower than you would with a higher-horsepowered car, to reach the same speed.
Translated: You might need a higher or lower dose of medication to get the same beneficial effect, depending on the individual.
This, in a nutshell, is what we mean by Personalized Medicine.
We’ll explore both aspects of pharmacogenomics (pharmacokinetics and pharmacodynamics) further in the next post.
Visit The Animated Genome Page!
Meanwhile, check out this beautifully done video below, from the Smithsonian National Museum of Natural History and the National Human Genome Research Institute: “The Animated Gene.” (Click on the image to go to the site.)
How about you? Have you tried any of these genotyping tests, for ADHD medications or for other purposes?
Did your physician initiate the testing and interpret for you? Was the information helpful?
Before pursuing the testing, did you/your prescriber follow a standard protocol for choosing medication?
Next post: Part 4:
All 7 Posts in this Series:
1. Explains genetic testing as it relates to ADHD medication-response
2. Dr. Goat and I share our ADHD genetic test results—and reactions
3. This Post: Defining the term genotyping, or genetic, test.
4. Explains how, when, and why this data might prove helpful
5. Reminds that genotyping data provides only one piece of the puzzle.
6. A closer look at Gina’s ADHD genetic testing results
7. Drilling down into Dr. Goat’s Results — to explain more about the data
We welcome your comments.