Tetrabenazine has been approved by the Food and Drug Administration (FDA) of the USA for the control of chorea - the jerky, uncontrollable movements that characterise Huntingdon's disease. The drug reduces the amount of dopamine around certain synapses, the junctions through which brain cells communicate with each other using dopamine as a chemical messenger. People with Huntington's have too much dopamine around certain types of brain cells, which leads to chorea, the jerkiness of movement.
The drug was tested in a randomized, double-blind, placebo-controlled multi-center clinical trial. Double blind means neither the patients nor the doctors knew if they were using the real drug or a placebo. Other studies supported the evidence of the trial, said the FDA.
Serious adverse reactions reported from trial use included depression and suicidal thoughts and behaviour, so the FDA advises that doctors should not use tetrabenazine in patients who have untreated depression or who are actively suicidal. Risk of suicide is a heightened concern when treating patients with Huntington's.
Other common side effects reported by patients in the trial include: insomnia, depression, drowsiness, restlessness and nausea. Also, although the trials showed the drug lessens chorea in the short term, it also caused worsening of mood, cognition, rigidity and functional capacity, so the FDA advises doctors and families of patients on the drug to pay attention to all the aspects of the disease.
The FDA has approved the drug with a required risk evaluation and mitigation strategy to ensure that side effects are correctly monitored and that patients are fully informed.
