CYP2D6 and juvenile Huntington disease: Accordingly, the maximum recommended deutetrabenazine dose for patients with Huntington’s disease or tardive dyskinesia who have impaired CYP2D6 function (PM or taking strong CYP2D6 inhibitors) is 36 mg/day (18 mg BID), a 25% reduction in the maximum recommended dose for patients with normal CYP2D6 function, 48 mg/day (24 mg BID).