Yes — the active ingredient is metabolized by a gene known to vary between individuals.
Relevant genes: CYP2D6
Used for: ADHD, binge eating disorderGene2Rx covers this medication using the same CPIC and FDA guidelines GeneSight uses, costs $5-$49 instead of several hundred, and works with your existing 23andMe data.
Vyvanse is lisdexamfetamine, a prodrug, meaning the pill you swallow is not the active medication. Red blood cells cleave off a lysine group in your bloodstream, releasing dextroamphetamine, which is what actually acts on your brain. That two-step activation is deliberate: it makes Vyvanse slow-onset, long-acting, and harder to misuse than immediate-release amphetamines. But it also means Vyvanse's pharmacogenetics are really the pharmacogenetics of dextroamphetamine once it's activated, and that's where the CYP2D6 gene enters the picture. CYP2D6 is the liver enzyme that clears dextroamphetamine out of your system, and it's one of the most variable genes in the human genome. That's why some people feel Vyvanse for 14 hours and others barely feel it at all.
Lisdexamfetamine itself has essentially no psychoactive effect. The clinical behavior of Vyvanse (how fast it kicks in, how long it lasts, how strong it feels) is determined by the activation step, which is fairly constant across people, and then by how fast CYP2D6 clears the released dextroamphetamine. Poor CYP2D6 metabolizers experience a much stronger and longer-lasting effect from a given Vyvanse dose and are more likely to report irritability, insomnia, or appetite suppression that lasts into the evening. Ultrarapid metabolizers often report that Vyvanse feels weaker than expected or wears off before the end of the work day.
Read the full lisdexamfetamine genetics guide →Published guidance from FDA on how lisdexamfetamine should be dosed or substituted based on your CYP2D6 phenotype.
| Phenotype | What it means | Recommendation | Evidence |
|---|---|---|---|
|
Ultrarapid Metabolizer
CYP2D6
|
Your body processes amphetamine faster than most people, but there is no specific FDA guidance for your genotype. The standard dose is typically used. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Normal Metabolizer
CYP2D6
|
Your body processes amphetamine at a normal rate. The standard dose should work as expected. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Intermediate Metabolizer
CYP2D6
|
Your body processes amphetamine slightly slower than average, but there is no specific FDA guidance for your genotype. The standard dose is typically used. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Poor Metabolizer
CYP2D6
|
Your body breaks down amphetamine much more slowly than normal, which may cause the drug to build up and increase your risk of side effects. A lower dose or a different medication may be needed. |
FDA
Consider a lower starting dose or an alternative medication due to increased risk of side effects.
|
Moderate |
|
Indeterminate
CYP2D6
|
The impact of your genotype on response to this drug is unknown |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Not available
CYP2D6
|
The impact of your genotype on response to this drug is unknown |
FDA
Initiate therapy with recommended starting dose.
|
— |
Source: FDA
CYP2D6 is the most clinically important pharmacogene. It metabolizes around a quarter of all prescription drugs, including many antidepressants, opioids, and stimulants. The gene is unusually variable: roughly 7 percent of people are poor metabolizers (they barely activate CYP2D6), and another 1 to 3 percent are ultrarapid metabolizers (their enzyme is overactive).
For most CYP2D6 drugs, poor metabolizers feel stronger effects and more side effects at standard doses, while ultrarapid metabolizers may feel almost nothing. For prodrugs like codeine, the relationship flips: poor metabolizers feel less effect because they can't activate the drug.
If you've tried multiple ADHD medications and Vyvanse either barely works or works too strongly, your CYP2D6 metabolizer phenotype is worth knowing. It won't change the decision to use a stimulant (that's between you and your prescriber), but it can explain why standard starting doses miss the mark in either direction. It can also guide the conversation about dose or whether to try a different stimulant class. Methylphenidate, which goes through a different pathway, is often tried when CYP2D6-mediated amphetamines misbehave.
Vyvanse (lisdexamfetamine) is a prodrug that releases dextroamphetamine in the bloodstream. Once released, the amphetamine follows the same metabolic pathway as any other amphetamine product, primarily through CYP2D6. So Vyvanse inherits amphetamine's pharmacogenetic profile, even though the pill itself is a different molecule.
The active drug is effectively the same once activation happens. Vyvanse becomes dextroamphetamine; Adderall is already a mix of amphetamine salts that includes dextroamphetamine. Both clear through CYP2D6. The differences between Vyvanse and Adderall are pharmacokinetic (how fast the drug reaches therapeutic levels), not pharmacogenetic.
Don't change your dose on your own. The practical implication is that a standard starting dose is likely to feel stronger and last longer than advertised for you, and your prescriber may want to start lower or space doses differently. Share your metabolizer status with them. Many psychiatrists now incorporate CYP2D6 results into dose decisions.
This page describes the general pharmacogenetics. A Gene2Rx report analyzes your own DNA to tell you which metabolizer group you fall into, across every medication.
Get your report Look up another medicationInformational only — not medical advice. Pharmacogenetic guidance describes population-level patterns; your individual response depends on many factors. Never start, stop, or change a medication without talking to your prescribing clinician.