The invention provides (+)-a-dihydrotetrabenazine succinate salt. Also provided are (+)-a-dihydrotetrabenazine succinate salt for use in medicine, pharmaceutical compositions comprising (+)-a-dihydrotetrabenazine succinate salt and a pharmaceutically acceptable excipient and the uses of (+)-a- dihydrotetrabenazine succinate salt as a VMAT2 receptor antagonist and in the treatment of a movement disorder such as Tourette's syndrome. The invention further provides a method for preparing the (+)-a-dihydrotetrabenazine succinate salt.
