Motetis (Tetrabenazine)

• Motetis (tetrabenazine) acts on the vesicular monoamine transporter 2 pathway to control abnormal involuntary movements.
• Huntington's disease (chorea): reduces the severity and frequency of choreiform movements, improving motor function.
• Tardive dyskinesia (drug‑induced involuntary movements): decreases the intensity of facial and limb dyskinesias.
• Other hyperkinetic movement disorders (off‑label): may provide symptomatic relief of involuntary movements.

• Tetrabenazine reversibly inhibits the vesicular monoamine transporter 2 (VMAT2) located on presynaptic neuronal vesicles. By blocking VMAT2, it prevents the uptake of dopamine, serotonin, norepinephrine and other monoamines into synaptic vesicles, leading to reduced cytoplasmic storage and subsequent depletion of these neurotransmitters in the central nervous system. The resulting decrease in dopaminergic transmission dampens the hyperkinetic activity that underlies chorea and dyskinetic movements.

Tetrabenazine may cause a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Nausea
• Fatigue
• Somnolence
• Dizziness
• Depression
• Weight loss

Serious or Rare Side Effects

• Severe depression or suicidal ideation
• QT interval prolongation leading to arrhythmia
• Neuroleptic malignant‑like syndrome
• Parkinsonism
• Hepatic toxicity
• Agranulocytosis

• When prescribing tetrabenazine, clinicians should observe several safety considerations.
• Monitor for depression: assess mood regularly and intervene promptly if worsening occurs.
• Assess cardiac function: obtain baseline ECG and monitor QT interval during therapy.
• Avoid abrupt discontinuation: taper dose under medical supervision to prevent withdrawal phenomena.
• Use caution in hepatic impairment: dose adjustment may be required based on liver function.
• Avoid concomitant MAO inhibitors: risk of hypertensive crisis and serotonin syndrome.
• Store at ambient temperature: keep in original container, protect from moisture and light.

Tetrabenazine interacts with several drug classes; awareness of these interactions helps prevent adverse events.

Major Interactions (Avoid)

• Concomitant MAO inhibitors: may cause hypertensive crisis.
• Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine): increase tetrabenazine plasma levels, raising toxicity risk.
• QT‑prolonging agents (e.g., quinidine, sotalol): additive risk of cardiac arrhythmias.

Moderate Interactions (Monitor Closely)

• Antidepressants (SSRIs, SNRIs): may enhance serotonergic effects.
• Antipsychotics (especially dopamine antagonists): may potentiate motor side effects.
• Other dopaminergic agents (e.g., levodopa): may reduce therapeutic efficacy.