Tetrabenazine

Tetrabenazine is a drug for the symptomatic treatment of hyperkinetic movement disorder and is marketed under the trade names Nitoman in Canada and Xenazine in New Zealand and some parts of Europe, and is also available in the USA as an orphan drug. On August 15, 2008 the U.S. Food and Drug Administration (FDA) approved the use of tetrabenazine to treat chorea associated with Huntington's disease (HD), the first in the US. The compound has been known since the 1950s. The effort for US FDA approval was led by Dr. Joseph Jankovic. According to a 2008 news report, "Americans with Huntington's who weren't Jankovic's patients ordered tetrabenazine from Canada if they could afford it. But the worsening exchange rate put the price out of reach for many. A recent check found Canadian Internet pharmacies selling generic 25-milligram pills for $1.75 or more each in U.S. currency, brand-name 25-mg pills for around $2.35 each." After the FDA approval, Dr. Jancovic said "I'm worried that the drug is just going to be too expensive" and initial pricing was $68.50 per 25 mg tablet.

Pharmacology
Tetrabenazine works mainly as a VMAT-inhibitor and as such promotes the early metabolic degradation of monoamines, in particular the neurotransmitter dopamine.

Uses
Tetrabenazine is used as a treatment, but not a cure for hyperkinetic disorders such as:
 * Huntington's Disease – specificially the chorea associated with it
 * Tourette syndrome and other tic disorders
 * Tardive dyskinesia, a serious and sometimes irreversible side effect of long-term use of many antipsychotics, mainly typical antipsychotics
 * Hemiballismus, spontaneous flinging limb movements due to contra-lateral subthalamic nucleus damage

Side effects
Because tetrabenazine is closely related to antipsychotics, many of its side effects are similar. Some of these include:
 * Akathisia (aka "restless pacing" – an inability to keep still, with intense anxiety when forced to do so)
 * Depression - the most common side effect, reported in roughly 15% of those who take the medication
 * Dizziness, drowsiness, insomnia, fatigue, nervousness and anxiety
 * Parkinsonism

Unlike many antipsychotics, tetrabenazine is not known to cause tardive dyskinesia.

Warnings

 * Because of the relatively high incidence of depression, it has been recommended that people with a history of depression avoid taking tetrabenazine.
 * The concomitant intake of MAO inhibitors is contraindicated.