How long does it take for Xenazine (tetrabenazine) to work?

It may take 2 to 3 weeks for you to notice an improvement in your chorea symptoms after you start taking tetrabenazine (Xenazine). Continue to take your medicine as directed by your doctor, even if you do not see improvements right away.

In one study, Xenazine showed a significant effect within three weeks on the Total Chorea Score when compared to a placebo (inactive) treatment (an average reduction of 4 vs. 2 units, respectively).

Contact you healthcare provider if you think the medicine is not working or you have concerns about side effects.

Xenazine Study Overview

In a 12-week long, randomized, placebo-controlled study of 84 patients with chorea of Huntington disease, patients receiving Xenazine started treatment at a dose of 12.5 mg/day. The dose was increased by 12.5 mg at weekly intervals until satisfactory control of chorea was achieved, intolerable side effects occurred, or until a maximal dose of 100 mg/day was reached.

The primary efficacy endpoint was the Total Chorea Score (measured as a change in the chorea score of the Unified Huntington Disease Rating Scale - UHDRS), which ranged from 0 to 4 (with 0 representing no chorea) for 7 different parts of the body (total score ranged from 0 to 28).

Overall, the Total Chorea Scores for Xenazine declined by 5 units during the maintenance phase, which was the average of Week 9 and Week 12 scores vs. baseline scores at the start of the study, compared to a reduction of 1.5 units for the placebo group. The endpoint change of 3.5 units was statistically significant (p<0.0001), and represented a clinically meaningful 24% reduction in chorea severity from baseline (the start of the study).

Percentage of patients achieving reductions of at least 10, 6, and 3 points from baseline to Week 12

• 3 unit reduction: Xenazine 69% vs. 23% placebo
• 6 unit reduction: Xenazine 50% vs. 7% placebo
• 10 unit reduction: Xenazine 19% vs. 3% placebo

A Physician-rated Clinical Global Impression (CGI) favored Xenazine, but measures of functional capacity, cognition and activities of daily living (such as bathing, dressing, eating, toileting) did not fully meet statistical significance.

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Study Side Effects

The most commonly reported side effects in at least 10% of patients (Xenazine vs. placebo, respectively) included*:

• sedation / somnolence - 31% vs. 3%
• insomnia (trouble sleeping) - 22% vs. 0%
• fatigue - 22% vs. 13%
• depression - 19% vs. 0%
• akathisia (restlessness) - 19% vs. 0 %
• anxiety or worsening anxiety - 15% vs. 3%
• fall - 15% vs. 13%
• nausea - 13% vs. 7%
• upper respiratory tract infection - 11% vs. 7%

Over 90% of patients who received Xenazine in the 12-week study experienced one or more adverse reactions (side effects) at any time during the study.

Dose escalation was stopped or the dose was reduced in 28 of 54 (52%) patients randomized to Xenazine. In all of the HD chorea studies of Xenazine (with 187 patients), one patient committed suicide, one attempted suicide, and six had suicidal ideation.

*Note: This is not a complete list of side effects reported with Xenazine use. If you have questions about side effects, contact your doctor right away. You can access more complete Xenazine side effect information here.

How long does a dose of Xenazine last for chorea?

Chorea symptoms may return within 12 to 18 hours after the last dose of Xenazine is taken. Xenazine has a short half-life of 5 to 7 hours (the time it takes for its blood concentration to reduce by one-half). Within 5 half-lives (25 to 35 hours), most of the drug will be eliminated.

In one placebo-controlled study when Xenazine treatment was stopped (washout phase), the Total Chorea Score rapidly returned to the baseline levels (Huntington chorea symptoms worsened to where they were before the study treatment started) within one week.

This is not all the information you need to know about Xenazine (tetrabenzine) for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.