tetrabenazine
Xenazine	Pharmaceutical company: Ovation Pharmaceuticals www.ovationpharma.com

Pharmacologic classification: monoamine depleter
Therapeutic classification: anti-chorea drug
Pregnancy risk category: C

AVAILABLE FORMS
Tablets: 12.5 mg, 25 mg

INDICATIONS AND DOSAGES
Chorea associated with Huntington's disease—
Adults: Initially, 12.5 mg P.O. daily in the morning. After 1 week, increase dose to 12.5 mg P.O. b.i.d. Titrate dose by 12.5 mg at weekly intervals, as needed. Maximum dose, 25 mg. If dose of 37.5 to 50 mg is needed, administer t.i.d. Patients requiring more than 50 mg/day should be genotyped for CYP2D6 metabolism.
ADJUST-A-DOSE: In patients who are extensive or intermediate CYP2D6 metabolizers, slowly titrate doses above 50 mg at weekly intervals by 12.5 mg as needed and tolerated. Maximum daily dose is 100 mg; maximum single dose, 37.5 mg. In patients who are poor CYP2D6 metabolizers, maximum daily dose is 50 mg; maximum single dose, 25 mg.

CONTRAINDICATIONS AND CAUTIONS
Contraindicated in patients who are actively suicidal and in those with depression who aren't receiving treatment or aren't being adequately treated. Contraindicated in those with hepatic impairment and in those receiving a monoamine oxidase (MAO) inhibitor or reserpine.
   Use cautiously in patients at risk for aspiration pneumonia. Avoid use in patients with congenital long QT syndrome and in those with a history of arrhythmias.

INTERACTIONS
Drug-drug. CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine): May increase metabolite exposure. Reduce tetrabenazine dose as directed.
Drugs that prolong QT interval (chlorpromazine, thioridazine, ziprasidone, moxifloxacin), class 1A antiarrhythmics (quinidine, procainamide), and class III antiarrhythmics (amiodarone, sotalol): May cause arrhythmias. Avoid use together.
Neuroleptic drugs (haloperidol, chlorpromazine, risperidone, olanzapine): May increase risk of neuroleptic malignant syndrome and extrapyramidal effects. Use together cautiously.
Reserpine: May increase effects of tetrabenazine. Wait 20 days after reserpine therapy before starting tetrabenazine.
MAO inhibitors: May increase risk of serious, sometimes fatal, adverse reactions. Avoid use together.

Drug-lifestyle. Alcohol: May increase sedative effects. Discourage use together.

ADVERSE REACTIONS
CNS: sedation, somnolence, insomnia, depression, anxiety, extrapyramidal symptoms, fatigue, falling, balance difficulty, parkinsonism, bradykinesia, dizziness, irritability, obsessive reaction, dysarthria, unsteady gait, headache.
GI: nausea, vomiting.
GU: dysuria.
Metabolic: decreased appetite.
Respiratory: upper respiratory infection, dyspnea, bronchitis.
Skin: head laceration, ecchymosis.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING.

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