Tetrabenazine

Overview
Tetrabenazine is a drug for the symptomatical treatment of hyperkinetic movement disorder and is marketed under the trade names Nitoman&reg; in Canada and Xenazine&reg; in New Zealand and some parts of Europe, and is also available in the USA as an orphan drug. The compound is known since the 1950s. Tetrabenazine works mainly as a VMAT-inhibitor and as such promotes the early metabolic degradation of the neurotransmitter dopamine.

Common 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's 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 subthalamic nucleus damage

Side effects
Because tetrabenazine is closely related to the 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
 * Parkinsonism

Unlike many of the antipychotics, tetrabenazine is not known to cause Tardive dyskinesia, and in fact can be an effective treatment for the antipsychotic-induced movement disorder.

Warnings

 * Because of the relatively high incidence of depression, it has been recommended that people with a history of depression avoid taking tetrabenazine. Research into this is ongoing however, and this warning may be dropped in the future.
 * The concomitant intake of MAO inhibitors is contraindicated.