The FDA ( Food and Drug Administration ) has approved Xenazine ( Tetrabenazine ) for the treatment of chorea in people with Huntington’s disease.
Chorea is the jerky, involuntary movement that occurs in people with this disease.

Xenazine is a new drug and is the first treatment of any kind approved in the United States for any symptom of Huntington’s disease. Currently there are no other drugs that are FDA-approved to treat chorea.

Serious side effects reported with use of Xenazine include depression and suicidal thoughts and actions. Xenazine should not be used in patients who are actively suicidal or in patients with untreated depression. Concerns about the risk of suicide are heightened in all patients with Huntington’s disease.

Huntington's disease is a rare, inherited neurological disorder affecting about 1 in 10,000 people in the United States. The disease results from genetically programmed degeneration of brain cells. The deterioration causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. Huntington’s disease is passed from parent to child through a gene mutation. Each child of a parent with the disease has a 50 percent chance of inheriting the mutation.
About 30,000 people in the United States have Huntington’s disease and another 200,000 are at risk of developing the condition. Symptoms commonly develop between ages 30 and 50. The disease progresses slowly and a person may live for another 15-20 years after the onset of symptoms.

Xenazine decreases the amount of dopamine available to work at relevant synapses in the brain. Dopamine is a chemical that communicates between certain nerve cells in the brain. In patients with Huntington’s disease, this system is overactive and results in the abnormal movements called chorea. Xenazine decreases the amount of dopamine available to interact with certain nerve cells, thereby decreasing the involuntary movements.

The effectiveness and safety of Xenazine was established primarily in a randomized, double-blind, placebo-controlled multi-center clinical trial. Patients treated with Xenazine had a significant improvement in chorea compared to patients treated with placebo. Other studies provided additional support for this effect.

The most common side effects reported by patients using Xenazine in clinical trials include insomnia, depression, drowsiness, restlessness and nausea.

While the drug has been shown to decrease chorea in the short-term, it also showed slight worsening in mood, cognition, rigidity, and functional capacity in clinical trials.

Xenazine has been approved with a required Risk Evaluation and Mitigation Strategy ( REMS ) to ensure that the benefits of the drug outweigh its risks, particularly the risks of depression and suicidal thoughts and actions. REMS is a strategy to manage a known or potential serious risk associated with a drug or biological product.

Source: FDA, 2008

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