Nurses Compass
Drug Guide
Tetrabenazine
Classification
Therapeutic: Antipsychotic, movement disorder agent
Pharmacological: Vesicular Monoamine Transporter 2 (VMAT2) inhibitor
FDA Approved Indications
- Huntington's disease chorea
Mechanism of Action
Tetrabenazine depletes dopamine, serotonin, norepinephrine, and histamine by inhibiting VMAT2, leading to decreased monoamine storage in presynaptic neurons, reducing excessive movement in chorea.
Dosage and Administration
Adult: Initial dose typically 12.5 mg once or twice daily; titrate gradually based on response and tolerability. Maintenance dose usually 50 mg/day in divided doses, up to a maximum of 100 mg/day.
Pediatric: Not approved for pediatric use.
Geriatric: Start at lower doses and titrate carefully due to increased sensitivity and risk of side effects.
Renal Impairment: Use with caution; no specific dose adjustments established.
Hepatic Impairment: Use contraindicated in severe hepatic impairment.
Pharmacokinetics
Absorption: Well absorbed orally.
Distribution: Widely distributed; crosses blood-brain barrier.
Metabolism: Primarily via hepatic aldehyde oxidase and cytochrome P450 enzymes.
Excretion: Metabolites excreted mainly in urine.
Half Life: Approximately 4-8 hours.
Contraindications
- Depression or history of suicidality
- Use concomitantly with reserpine or monoamine oxidase inhibitors (MAOIs).
Precautions
- Monitor for depression, suicidality, or worsening Parkinsonian symptoms. Use with caution in patients with cardiac or psychiatric comorbidities.
Adverse Reactions - Common
- Hypotension (Common)
- Sedation/drowsiness (Common)
- Parkinsonism or other movement disorders (Common)
- Somnolence (Common)
- Decreased blood cell counts (e.g., akathisia, depression) (Uncommon)
Adverse Reactions - Serious
- Suicidal thoughts or behavior (Rare)
- Neuroleptic malignant syndrome (Rare)
- Hepatotoxicity (Rare)
Drug-Drug Interactions
- Antidepressants (risk of neuroleptic malignant syndrome)
- Reserpine and other centrally acting dopamine-depleting agents
- MAOIs (risk of hypertensive crisis)
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor mood, suicidal ideation, movement symptoms, blood pressure, and CBC regularly.
Diagnoses:
- Risk for suicidal behavior
- Ineffective coping related to movement disorder or side effects
Implementation: Start at low dose, titrate carefully, monitor for adverse effects, especially depression and movement changes.
Evaluation: Assess symptom control and side effects; adjust dose accordingly.
Patient/Family Teaching
- Do not stop medication abruptly.
- Report any mood changes, suicidal thoughts, or worsening symptoms.
- Monitor blood pressure regularly.
- Avoid alcohol and other CNS depressants.
Special Considerations
Black Box Warnings:
- Increased risk of depression and suicidality.
- Use caution in patients with a history of depression.
Genetic Factors: Genetic variations may influence metabolism and response.
Lab Test Interference: May cause false-positive results in urine catecholamine tests.
Overdose Management
Signs/Symptoms: Drowsiness, sedation, hypotension, extrapyramidal symptoms.
Treatment: Supportive care, monitoring vital signs, and symptomatic treatment. No specific antidote.
Storage and Handling
Storage: Store at room temperature, away from moisture and light.
Stability: Stable under proper storage conditions.