Tetrabenazine
Generic Details
Generic Name
Tetrabenazine
Other Names
- Xenazine
Drug Class
- Vesicular monoamine transporter 2 (VMAT2) inhibitor
Chemical Formula
C19H27NO3
Molecular Weight
317.42 g/mol
Mechanism of Action
- Tetrabenazine reversibly inhibits VMAT2, which leads to the depletion of dopamine, norepinephrine, and serotonin from nerve terminals.
Indications
- Huntington's chorea
- Tardive dyskinesia
Common Dosage Forms
- Tablet
Typical Dosage
- 25 mg once daily, may increase to 37.5 mg after 1 week, then increase to a maximum of 50 mg every week if needed
Pediatric Dosage
- Safety and efficacy not established in children
Geriatric Dosage
- Dose adjustments may be necessary due to age-related decrease in hepatic and renal function
Side Effects
- Drowsiness
- Insomnia
- Depression
- Restlessness
- Parkinsonism-like symptoms
Contraindications
- Concomitant use of monoamine oxidase inhibitors (MAOIs)
Pregnancy Category
- C - Risk cannot be ruled out
Lactation Safety
- Caution advised as tetrabenazine is excreted in human milk
Drug Interactions
- Concomitant use of reserpine may increase the risk of depression and parkinsonism-like symptoms
Overdose Symptoms
- Extreme sedation
- Hypotension
- Extrapyramidal symptoms
Antidote for Overdose
- There is no specific antidote, manage symptoms supportively
Storage Conditions
- Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C to 30°C (59°F to 86°F)
Pharmacokinetics
- Absorption: Rapidly absorbed after oral administration
- Distribution: Extensively distributed in the body, crosses the blood-brain barrier
- Metabolism: Primarily hepatic via CYP2D6 and CYP2C19
- Excretion: Mainly via urine
Precautions
- Caution in patients with hepatic impairment
- May cause drowsiness, caution while driving or operating machinery
Warnings
- Risk of depression and suicidal thoughts
- May worsen symptoms in patients with untreated or inadequately treated depression
Others
- Avoid abrupt discontinuation due to risk of neuroleptic malignant syndrome (NMS)