VMAT2 inhibitors (vesicular monoamine transporter-2 inhibitors) are used to treat movement disorders such as Huntington’s disease or tardive dyskinesia. In Huntington’s disease the uncontrollable movements may start out mild as fidgeting or quick movements of the feet and hands and then, as the disease progresses, the movements can become bigger and can involve flailing of arms and legs. Tardive dyskinesias are involuntary, repetitive body movements that can develop as a side effect of long term use of a group of medicines called neuroleptics. VMAT2 inhibitors reduce unwanted body movements for these conditions.