Yes — the active ingredient is metabolized by a gene known to vary between individuals.
Relevant genes: CYP2D6
xenazine is affected by pharmacogenetics through the CYP2D6 gene. Your genotype for this gene can change how your body processes xenazine, which can affect both how well it works and how well you tolerate it. The strongest evidence level on this page is Strong, based on CPIC or FDA guidelines.
Published guidance from FDA on how tetrabenazine should be dosed or substituted based on your CYP2D6 phenotype.
| Phenotype | What it means | Recommendation | Evidence |
|---|---|---|---|
|
Ultrarapid Metabolizer
CYP2D6
|
Your body processes tetrabenazine faster than average, but no specific dosing changes are recommended. The standard dose should work as expected. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Normal Metabolizer
CYP2D6
|
Your body processes tetrabenazine at a normal rate. The standard dose should work as expected. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Intermediate Metabolizer
CYP2D6
|
Your body processes tetrabenazine slightly slower than average, but no specific dosing changes are recommended at this time. |
FDA
Initiate therapy with recommended starting dose.
|
— |
|
Poor Metabolizer
CYP2D6
|
Your body breaks down tetrabenazine much more slowly than normal, causing the drug to reach higher levels in your system. A lower maximum dose is required to avoid side effects. |
FDA
Use a reduced dosage. The maximum recommended single dose is 25 mg and should not exceed 50 mg/day.
|
Strong |
|
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).
The v4 report preserves the activity score used in its interpretation. Some medicines use a combined CYP2D6/CYP2C19 recommendation. CYP2D6 inhibitors can change functional metabolism; a genotype alone does not capture that effect.
Browse the full drug-class: Movement disorder medications.
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.