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VMAT2 Inhibitor — Hyperkinetic Movement Disorders Pregnancy: Avoid — limited data; potential fetal harm

Tetrabenazine

Brand names: Nitoman

Adult dose

Dose: 12.5 mg once daily initially; titrate by 12.5 mg every week
Route: Oral
Frequency: 2–3 times daily (titrated)
Max: 200 mg/day (doses >50 mg/day need CYP2D6 genotyping in some guidelines)
Titrate slowly to effect. Doses above 50 mg/day: divide into 3 doses. CYP2D6 poor metabolisers — reduce dose. Monitor for depression and suicidality — black box warning. Avoid abrupt withdrawal (rebound chorea).

Paediatric dose

Route:
Seek specialist opinion — limited paediatric data; used in some paediatric movement disorder centres

Dose adjustments

Renal

Use with caution in severe renal impairment — limited data

Hepatic

Contraindicated in hepatic impairment — extensive hepatic metabolism

Clinical pearls

  • Mechanism: depletes presynaptic dopamine, serotonin, noradrenaline by inhibiting VMAT2 — reduces involuntary movements in Huntington's, hemiballismus, tardive dyskinesia
  • Deutetrabenazine (not available UK) and valbenazine are newer VMAT2 inhibitors with better tolerability
  • Screen for depression before and during treatment — Huntington's patients already at high suicide risk
  • Halve dose if CYP2D6 poor metaboliser phenotype confirmed
  • Consider dose reduction or switch if parkinsonism or depression emerges

Contraindications

  • Active or inadequately treated depression
  • Suicidal ideation
  • Hepatic impairment
  • Concurrent MAOI use
  • Concurrent reserpine use

Side effects

  • Depression and suicidality (black box warning)
  • Sedation
  • Akathisia
  • Parkinsonism
  • Insomnia
  • Nausea
  • Dysphagia
  • QTc prolongation (at high doses)
  • Neuroleptic malignant syndrome (rare)

Interactions

  • MAOIs — absolute contraindication (hypertensive crisis)
  • Reserpine — additive VMAT2 inhibition
  • CYP2D6 inhibitors (fluoxetine, paroxetine) — increase plasma levels, reduce dose
  • Antipsychotics — additive extrapyramidal effects
  • QT-prolonging drugs — additive risk

Monitoring

  • Depression/suicidality assessment at each visit
  • ECG if high dose or QT risk factors
  • Movement disorder rating scales (UHDRS)
  • LFTs baseline

Reference: BNFc; BNF 90; NICE NG42 (Huntington's Disease); TETRA-HD Trial; MHRA SPC Nitoman. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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