Tetrabenazine (TBZ) is type 2 (VMAT2) selective obstruction medicines for vesicular monoamine transporter (VMAT), and VMAT2 of a central nerve is obstructed strong, it reduces monoamine (Dopamine (DA), noradrenalin (NA) and serotonin (5-HT)) nervous communication. After TBZ was given to a microorganism, due to the first pass, metabolism is done in the isomer of α - and β- dihydrotetrabenazine (HTBZ) but as α - and β -HTBZ possess equal VMAT2 obstruction activity, it is considered that effect by the shape the metabolism or the unaltered substance will be shown. TBZ decrease the monoamine amount (striata) in the rat brain promptly, and the DA selectivity was admitted by the action. This action became biggest in 15 min after prescription and continued for 2 h. It was difficult for medicine-proof to occur to a monoamine drying action of TBZ. It is guessed that the involuntary movement such as chorea which is one of the symptoms in an early stage of Huntington disease (Huntington's disease: HD) patient is caused by 'Direct path superiority' (dopamine D and (D1) receptor function rise) of basal ganglion. It is considered that TBZ express the effect by the control of D1 receptor function. TBZ also showed the validity in an HD model animal. TBZ undergoes metabolic change to α - and β-HTBZ by a man liver. It was done presumed to undergo metabolic change to 9 -, 10 - desmethyl α-HTBZ, 9 - and 10 -desmethyl α- HTBZ after that. When TBZ is orally administered in an healthy adult orally, a - HTBZ and α - HTBZ which are active metabolite and concentration of plasma level of the main metabolite 9 - desmethyl β- HTBZ achieved a high concentration in the blood plasma within two hours after administration, and dose linearity was confirmed by the amount of disclosure. On the other hand, plasma level of TBZ changed low, and almost no blood plasma was detected in 4 h after administration. In the third clin. study that was executed targeting the HD patients inside and outside the country, a significance improvement of Chorea total score (TCS) was confirmed by the administration of TBZ and its improvement effect was maintained in long time administration. As above, in the country there were no curatives which make the HD adaptation, but it is expected that TBZ is useful for living quality (quality of life : QOL) improvement of an HD patient as the only curative in the country with disease for which the medicine is efficacious of Chorea with HD.