Xenazine is the first drug to treat chorea in Huntington's disease

Key Points

"Within a few months, for the first time, physicians will be able to offer these critically-ill patients a safe and effective medication to treat their chorea," says Fred Marshall, MD, chief of the geriatric neurology unit at the University of Rochester.

Huntington's disease is an inherited neurological disorder affecting about one in 10,000 people in the United States. Today, about 30,000 Americans have Huntington's disease. The disease results from a genetically programmed degeneration of brain cells that causes uncontrolled movements, loss of intellectual faculties and emotional disturbance. Symptoms develop between ages 30 and 50. The disease progresses slowly, and a person may live for another 15 to 20 years after the onset of symptoms.

Xenazine has been designated an orphan drug by the FDA and will have market exclusivity in the United States for seven years. Xenazine's FDA approval was based on results from 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 a placebo. The drug received marketing clearance with a required Risk Evaluation and Mitigation Strategy (REMS) to ensure the benefits of the drug outweigh its risks, particularly with regard to depression and suicide.

The REMS includes educational materials, such as a medication guide, for prescribers, pharmacists, and patients (and their caregivers) to help minimize adverse effects associated with the drug. Xenazine is available in 12.5 mg or 25 mg tablets. At first, therapy should be titrated up slowly by 12.5 mg at weekly intervals to allow the identification of a dose that reduces chorea and that the patient will tolerate well. This dose of 12.5 mg per day is 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. If a dose of 37.5 to 50 mg per day is needed, it should be given in a regimen of three doses a day. The dosing recommendation is up to 50 mg per day, with a maximum recommended single dose of 25 mg.

In clinical trials, the most common side effects reported by patients included insomnia, depression, drowsiness, restlessness and nausea. Serious side effects included depression and suicidal thoughts and actions. While the drug has been shown to decrease chorea in the short term. It also showed a slight worsening in mood, cognition, rigidity, and functional capacity.

Healthcare professionals and family members of patients taking the drug are advised to monitor all aspects of the disease.

TIPS TO REMEMBER Xenazine

Lisa B. Samalonis is a medical writer from Gloucester Township, NJ.