Nitoman (Tetrabenazine)

Nitoman (tetrabenazine) acts on the vesicular monoamine transporter 2 pathway to treat specific movement disorders.

• Huntington's disease (chorea): reduces the frequency and severity of involuntary choreiform movements, helping to improve overall motor function and patient quality of life.
• Tardive dyskinesia: lessens repetitive, involuntary facial grimacing and limb motions, providing symptomatic relief for patients with medication‑induced movement disorders.

• Tetrabenazine selectively inhibits vesicular monoamine transporter 2 (VMAT2) in presynaptic neurons, preventing the uptake of dopamine, serotonin, norepinephrine and other monoamines into synaptic vesicles. This blockade reduces the amount of neurotransmitter released into the synaptic cleft, leading to decreased dopaminergic stimulation of postsynaptic receptors, which mitigates hyperkinetic movement symptoms associated with Huntington's disease and tardive dyskinesia.

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

Common Side Effects

• Drowsiness: feeling unusually sleepy or sluggish.
• Fatigue: persistent lack of energy affecting daily activities.
• Nausea: upset stomach often accompanied by an urge to vomit.
• Depression: low mood or loss of interest that may require monitoring.

Serious or Rare Side Effects

• Neuroleptic malignant syndrome: rare but life‑threatening reaction with fever, muscle rigidity, and autonomic instability.
• Suicidal thoughts: emergence or worsening of suicidal ideation requiring immediate medical attention.

When prescribing tetrabenazine, clinicians should observe several safety considerations.

• Assess baseline mood: monitor for depression or suicidal thoughts before initiating therapy.
• Evaluate liver function: check hepatic enzymes as tetrabenazine is metabolized hepatically.
• Review concomitant medications: avoid drugs that prolong QT interval or affect CYP2D6 metabolism.
• Adjust dose in renal impairment: consider lower starting dose for patients with reduced renal clearance.
• Monitor cardiac status: obtain ECG if patient has cardiac risk factors or is on QT‑prolonging agents.
• Store at ambient temperature: keep below 25 °C, in the original container, protected from moisture and light.

Tetrabenazine interacts with several drug classes, requiring careful management to avoid adverse outcomes.

Major Interactions (Avoid)

• Strong CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, quinidine): can markedly increase tetrabenazine plasma levels, raising risk of toxicity.
• QT‑prolonging agents (e.g., haloperidol, sotalol): combined use may exacerbate cardiac rhythm disturbances.

Moderate Interactions (Monitor Closely)

• CYP2D6 substrates (e.g., codeine, tramadol): may have altered efficacy when co‑administered.
• Antidepressants affecting serotonin (e.g., SSRIs): monitor for additive central nervous system depression.
• Antipsychotics (e.g., risperidone): may require dose adjustments to balance therapeutic effects.