Tetrabenazine

Available brands

Indications

Tetrabenazine is indicated for the treatment of chorea associated with Huntington's disease,

Pharmacology

Tetrabenazine is a drug formerly used as an antipsychotic but now used primarily in the symptomatic treatment of various hyperkinetic disorders, It is a vesicular monoamine transporter-2 (VMAT-2) inhibitor that used as symptomatic treatment of chorea associated with Huntington's disease.

Dosage & Administration

Recommended dosing for Tetrabenazine: Tetrabenazine can be taken with or without food. Individualization of dose with careful weekly titration is required.

1st week's starting dose: 12.5 mg daily.
2nd week: 25 mg (12.5 mg twice daily).
Then slowly titrate at weekly intervals by 12.5 mg to a tolerated done that reduces chorea. Doses of 37.5 mg and up to 50 mg per day should be administered in three divided doses per day with a maximum recommended single dose not to exceed 25 mg.
Patients requiring doses above 50 mg per day should be genotyped for the drug-metabolizing enzyme CYP2D6 to determine if the patient is a poor metabolizer or an extensive metabolizer.
Maximum daily dose in poor metabolizers: 50 mg with a maximum single dose of 25 mg.
Maximum daily dose in Extended and intermediate metabolizers: 100 mg with a maximum single dose of 37.5 mg.
If serious adverse reactions occur, titration should be stopped and the dose should be reduced. If the adverse reactions do not resolve, consider withdrawal of Tetrabenazine.

Pediatric & geriatric use: Safety and effectiveness in pediatric patients have not been established. The pharmacokinetics of Tetrabenazine and its primary metabolites have not been formally studied in geriatric subjects.

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Interaction

With medicine: Strong CYP2D6 Inhibitors: A reduction in Tetrabenazine dose may be necessary when adding a strong CYP2D6 inhibitor (e.g., fluoxetine, paroxetine, quinidine) in patients maintained on a stable dose of Tetrabenazine.

Reserpine: Reserpine binds irreversibly to VMAT2, and the duration of its effect is several days. At least 20 days should elapse after stopping reserpine before starting Tetrabenazine, Tetrabenazine and Reserpine should not be used concomitantly.

With food & others: No interaction with food, can be taken with or without food.

Contraindications

Tetrabenazine is contraindicated in:

Actively suicidal, or who have depression which is untreated or undertreated Hepatic impairment.
Concurrent use of monoamine oxidase inhibitors (MAOIs) or reserpine.
Concurrent use of deutetrabenazine or valbenazine.

Side Effects

Common: Most common adverse reactions (>10% and at least 5% greater than placebo) were-Sedation/somnolence, fatigue, insomnia, depression, akathisia, anxiety/anxiety aggravated & nausea.

Rare: Suicidal thoughts, neuroleptic malignant syndrome, a reaction characterized by fever, muscle rigidity and confusion & pneumonia.

Pregnancy & Lactation

There are no adequate data on the developmental risk associated with the use of Tetrabenazine in pregnant women. There are no data on the presence of tetrabenazine or its metabolites in human milk.

Precautions & Warnings

The benefit and potential for adverse effects such as worsening mood, cognition, rigidity, and functional capacity should be periodically re-evaluated. The maximum daily dose should not exceed 50 mg/day and the maximum single dose should not exceed 25 mg if administered in conjunction with a strong CYP2D6 inhibitor (e,g., fluoxetine, paroxetine). In case of Neuroleptic Malignant Syndrome, the treatment should be discontinued. The dose should be reduced or discontinued if patient experience restlessness, agitation, akathisia and parkinsonism, The treatment may impair patient's ability to drive or operate complex machinery, Tetrabenzine is not recommended in combination with other drugs that prolong QTc.