Indications

Tetrazin is indicated for the symptomatic treatment of chorea associated with Huntington's disease.

Pharmacology

Tetrabenazine is a Vesicular Monoamine Transporter-2 (2VMAT-2) inhibitor.3 By inhibiting 4VMAT-2, it reduces the transport and release of monoamine neurotransmitters (like dopamine) into the synapse, which helps in managing hyperkinetic disorders like chorea.

Dosage & Administration (Oral)

Dosing requires individualization and careful weekly titration. It can be taken with or without food.

• Maximum Daily Dose (Genotyping Required for High Doses):

  • Poor Metabolizers (): 

  • Extensive/Intermediate Metabolizers ():  (Max single dose: )  

  • Adverse Reactions: If serious reactions occur, stop titration or reduce the dose.

Contraindications

Tetrabenazine is contraindicated in patients who are:

• Actively suicidal, or have untreated/undertreated depression.  

• Have hepatic impairment.

• Using monoamine oxidase inhibitors (), reserpine, deutetrabenazine, or valbenazine concurrently.

Side Effects

The most common adverse reactions (≥10%) include:

• Sedation/somnolence

• Fatigue

• Insomnia

• Depression

• Akathisia(inner restlessness)  

• Anxiety and nausea.

  Rare but serious reactions include suicidal thoughts and Neuroleptic Malignant Syndrome (NMS).

Precautions & Warnings

• Depression/Suicidality: Mood, cognition, and functional capacity should be periodically re-evaluated.

• Drug Interactions: Dose reduction may be necessary if co-administered with a strong inhibitor(e.g., fluoxetine, paroxetine).  

• QTc Prolongation:Not recommended in combination with other drugs that prolong the interval.  

• Driving/Operating Machinery: Treatment may impair the ability to drive or operate complex machinery.

• NMS: Discontinue the treatment if (fever, muscle rigidity, confusion) is suspected.

Therapeutic Class: Atypical neuroleptic drugs.

Storage: Store in a cool and dry place, protected from light and moisture.