Atrest
✅ Reduces involuntary movements
✅ Controls chorea symptoms
✅ Enhances motor function
✅ Improves quality of life
✅ Minimizes muscle spasms
Atrest contains Tetrabenazine.
✓ Medically reviewed by Morgan Ellis — Pharmacy Researcher · 8 years experience · Last reviewed: May 2026
⚡ Quick Answer — What is Atrest?
Atrest is an oral tetrabenazine (12.5 mg) tablet — a VMAT2 (vesicular monoamine transporter 2) inhibitor specifically approved for the treatment of chorea associated with Huntington disease. It works by depleting dopamine from nerve terminals, reducing the involuntary writhing and jerking movements that characterise Huntington chorea. Starting dose: 12.5 mg once daily, increased weekly by 12.5 mg to a maximum of 37.5 mg/dose (75–100 mg/day), always divided into 2–3 doses. Patients receiving >50 mg/day require CYP2D6 genotyping. Common side effects: sedation, akathisia, depression, parkinsonism, insomnia. Black-box warning: increases risk of depression and suicidality in Huntington patients — monitor mood closely.
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What Is Atrest?
Atrest is an oral tablet containing tetrabenazine 12.5 mg. Tetrabenazine is a vesicular monoamine transporter 2 (VMAT2) inhibitor — the first drug specifically approved for the treatment of chorea associated with Huntington disease.
By depleting presynaptic dopamine stores, tetrabenazine reduces the involuntary, dance-like movements (chorea) that characterise Huntington disease without the tardive dyskinesia risk of traditional dopamine receptor blockers. It was first used in Europe in the 1970s and gained FDA approval in 2008 as Xenazine. Atrest is manufactured by a WHO-GMP certified facility and is bioequivalent to the originator brand at the same strength.
How Does Atrest (Tetrabenazine) Work?
Tetrabenazine irreversibly inhibits VMAT2, the protein responsible for packaging dopamine, serotonin, and norepinephrine into synaptic vesicles. By blocking VMAT2, the drug depletes presynaptic monoamine stores — predominantly dopamine in the basal ganglia. Excessive dopaminergic activity in the striatum is the primary driver of choreiform movements in Huntington disease, so reducing dopamine availability at the post-synaptic receptor directly suppresses chorea.
The drug is extensively metabolised by CYP2D6 into two active metabolites (α-HTBZ and β-HTBZ) that account for most of the clinical effect. CYP2D6 poor metabolisers have significantly higher plasma levels, which is why genotyping is required before exceeding 50 mg/day.
Dosing and Administration
| Week | Daily Dose | Schedule |
|---|---|---|
| Week 1 | 12.5 mg | Once daily (morning) |
| Week 2 | 25 mg | 12.5 mg twice daily |
| Week 3+ | 37.5–50 mg | Divided into 2–3 doses |
| Maximum | 75–100 mg/day* | *CYP2D6 genotyping required >50 mg/day |
Take with or without food. No single dose should exceed 37.5 mg. If treatment is interrupted for >5 days, re-titrate from 12.5 mg.
Side Effects
Common (≥10%): sedation/somnolence, fatigue, insomnia, depression, akathisia (restlessness), anxiety, nausea.
Serious: parkinsonism (dose-related), neuroleptic malignant syndrome (rare), QTc prolongation (avoid in congenital long-QT syndrome), dysphagia (increased aspiration risk in Huntington patients).
Warnings and Precautions
- Depression and suicidality — FDA black-box warning. Tetrabenazine increases the risk of depression and suicidal ideation/behaviour in Huntington disease patients, who already have a high baseline suicide rate (~5–10%). Assess for depression before starting. Discontinue if depression worsens or suicidal thoughts emerge.
- Neuroleptic malignant syndrome (NMS). Rare but reported. Suspect NMS if the patient develops hyperthermia, rigidity, altered consciousness and autonomic instability. Discontinue immediately.
- Parkinsonism. Dopamine depletion can cause bradykinesia, rigidity, tremor and falls. Dose-related — reduce the dose if parkinsonian features appear.
- Dysphagia. Tetrabenazine can worsen swallowing difficulty, which is already a concern in Huntington disease. Aspiration risk increases. Monitor and consider speech-therapy assessment.
- QTc prolongation. At doses >50 mg/day, tetrabenazine prolongs the QT interval. ECG monitoring recommended at higher doses. Avoid combination with other QTc-prolonging drugs.
- CYP2D6 poor metabolisers. Tetrabenazine is extensively metabolised by CYP2D6. Poor metabolisers have higher plasma levels and increased toxicity. Maximum dose in CYP2D6 PMs is 50 mg/day (vs 100 mg/day in EMs). CYP2D6 genotyping is recommended before exceeding 50 mg/day.
- Hepatic impairment. Contraindicated in patients with hepatic impairment (no dose-adjustment data available).
- Driving. Sedation, akathisia and parkinsonism can impair driving. Avoid until stable on dose.
Contraindications — Who Should NOT Take Atrest
- Actively suicidal or inadequately treated depression
- Hepatic impairment
- Concurrent use of MAO inhibitors (hypertensive crisis risk)
- Concurrent use of reserpine (additive dopamine/serotonin depletion)
- Known hypersensitivity to tetrabenazine or any excipient
Drug Interactions
- MAO inhibitors: Contraindicated — risk of hypertensive crisis. Wait ≥14 days after stopping an MAOI before starting tetrabenazine.
- Strong CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine): Increase tetrabenazine exposure — dose reduction required.
- Reserpine: Contraindicated — additive monoamine depletion. Wait ≥20 days between agents.
- Dopamine antagonists (antipsychotics, metoclopramide): Additive parkinsonism and akathisia risk.
- Alcohol & CNS depressants: Enhanced sedation — avoid or use cautiously.
Storage Instructions
- Store at room temperature, 15–30°C. Protect from moisture.
- Keep in original packaging until use.
- Keep out of reach of children.
- Do not use after the expiry date.
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Frequently Asked Questions
What is Atrest used for?
Atrest contains tetrabenazine 12.5 mg and is used to treat chorea (involuntary movements) associated with Huntington disease. It is the first drug specifically approved for this indication. It may also be used off-label for tardive dyskinesia and other hyperkinetic movement disorders.
How long does tetrabenazine take to reduce chorea?
Chorea reduction is typically noticeable within 1–2 weeks of reaching a therapeutic dose during titration. The TETRA-HD trial showed a significant reduction in chorea scores after a mean maintenance dose of ~50 mg/day over 12 weeks.
Why does tetrabenazine require CYP2D6 genotyping?
Tetrabenazine is metabolised by CYP2D6 into active metabolites. Poor metabolisers (5–10% of Caucasians) have significantly higher drug exposure and are at greater risk of adverse effects. Genotyping is required before exceeding 50 mg/day to set a safe dose ceiling.
Can I stop Atrest suddenly?
Abrupt discontinuation is generally well-tolerated (chorea returns but does not rebound beyond baseline). However, if you have been on the drug for months, a gradual taper over 1–2 weeks is prudent to monitor for mood changes. If interrupted for >5 days, re-titrate from 12.5 mg.
What is the difference between tetrabenazine and deutetrabenazine?
Deutetrabenazine (Austedo) is the deuterated form — the same molecule with deuterium atoms replacing hydrogen at key positions. This slows CYP2D6 metabolism, resulting in longer half-life, lower peak levels, and twice-daily dosing instead of three times daily. Deutetrabenazine also carries a lower incidence of somnolence in trials.
Does tetrabenazine cause parkinsonism?
Yes — because it depletes dopamine, it can produce dose-related parkinsonian symptoms (bradykinesia, rigidity, tremor). This usually resolves with dose reduction. The goal is to find the lowest dose that adequately controls chorea without producing parkinsonism.
Is Atrest the same as Xenazine?
Both contain tetrabenazine. Xenazine is the original brand manufactured by Lundbeck. Atrest is a generic-equivalent tablet with the same active ingredient, strength (12.5 mg), and bioavailability at a lower cost.
Can tetrabenazine be used for tardive dyskinesia?
Tetrabenazine is used off-label for tardive dyskinesia (TD) and has shown benefit in case series and small trials. However, valbenazine (Ingrezza) and deutetrabenazine (Austedo) are specifically FDA-approved for TD and are generally preferred.
Can I drink alcohol while taking Atrest?
Alcohol adds to the sedation and CNS-depressant effects of tetrabenazine. It also worsens depression — a significant concern given the black-box warning. Avoid alcohol or limit intake significantly.
What should I do if I miss a dose?
Take the missed dose as soon as you remember, unless it is almost time for the next dose. Do not double up. If you miss doses for 5 or more consecutive days, contact your prescriber — re-titration from the starting dose may be necessary.
Does Atrest interact with antidepressants?
SSRIs and SNRIs that strongly inhibit CYP2D6 (fluoxetine, paroxetine) will increase tetrabenazine levels — dose adjustment is required. Weaker CYP2D6 inhibitors (sertraline, citalopram, escitalopram) are safer choices if an antidepressant is needed alongside tetrabenazine.
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| Strength | 12.5 mg |
|---|---|
| Quantity | 10 Tablet/s, 30 Tablet/s, 60 Tablet/s, 90 Tablet/s, 180 Tablet/s |
Atrest
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