<p>General Dosing Considerations:</p>

<p>The chronic daily dose of Tetrabenazine used to treat chorea associated with Huntington&#39;s disease (HD) is determined individually for each patient. When first prescribed, Tetrabenazine therapy should be titrated slowly over several weeks to identify a dose of XENAXINE that reduces chorea and is tolerated. Tetrabenazine can be administered without regard to food.<br />
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<p>Individualization Of Dose:</p>

<p><strong>Dosing Recommendations Up to 50 mg per day</strong>: The starting dose should be 12.5 mg per day given once in the morning. After one week, the dose should be increased to 25 mg per day given as 12.5 mg twice a day. Tetrabenazine should be titrated up slowly at weekly intervals by 12.5 mg daily, to allow the identification of a tolerated dose that reduces chorea. If a dose of 37.5 to 50 mg per day is needed, it should be given in a three times a day regimen. The maximum recommended single dose is 25 mg. If adverse reactions such as&nbsp;akathisia, restlessness,&nbsp;parkinsonism, depression, insomnia, anxiety or sedation occur, titration should be stopped and the dose should be reduced. If the adverse reaction does not resolve, consideration should be given to withdrawing Tetrabenazine treatment or initiating other specific treatment (e.g.,&nbsp;antidepressants).<br />
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<strong>Dosing Recommendations Above 50 mg per day</strong>: Patients who require doses of Tetrabenazine greater than 50 mg per day should be first tested and genotyped to determine if they are poor metabolizers (PMs) or extensive metabolizers (EMs) by their ability to express the drug metabolizing enzyme, CYP2D6. The dose of Tetrabenazine should then be individualized accordingly to their status as PMs or EMs<br />
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<p>Extensive and Intermediate CYP2D6 Metabolizers:</p>

<p>Genotyped patients who are identified as extensive (EMs) or intermediate metabolizers (IMs) of CYP2D6, who need doses of Tetrabenazine above 50 mg per day, should be titrated up slowly at weekly intervals by 12.5 mg daily, to allow the identification of a tolerated dose that reduces chorea. Doses above 50 mg per day should be given in a three times a day regimen. The maximum recommended daily dose is 100 mg and the maximum recommended single dose is 37.5 mg. If adverse reactions such as akathisia, parkinsonism, depression, insomnia, anxiety or sedation occur, titration should be stopped and the dose should be reduced. If the adverse reaction does not resolve, consideration should be given to withdrawing Tetrabenazine treatment or initiating other specific treatment (e.g., antidepressants)</p>