Of what use is tetrabenazine in the treatment of Huntington disease?

Tetrabenazine is a vesicular monoamine transporter 2 (VMAT2) inhibitor approved in Canada, Europe, and the USA to treat involuntary movements associated with Huntington disease.

By blocking the VMAT2, it reduces the storage of monoamines (predominantly dopamine and serotonin) into presynaptic vesicles and hence decreases their release into the synaptic cleft, thereby reducing excessive neurotransmission.