(2R,3S,11bS) -Dihydrotetrabenazine

(2R,3S,11bS) -9,10-dimethoxy-3- (2-methylpropyl) -1H,2H,3H,4H,6H,7H,11bH-pyrido[2,1-a]isoquinolin-2-ol is an impurity of Tetrabenazine, which is a VMAT inhibitor used in the treatment of hyperkinetic movement disorder.