This is a Phase 1, open-label, parallel-group, single-dose study of lofexidine in 6 adult subjects with mild hepatic impairment (Child Pugh score of 5 6), 6 adult subjects with moderate hepatic impairment (Child Pugh score 7 9), 6 adult subjects with severe hepatic impairment (Child Pugh score 10 15), and 6 control subjects with normal hepatic function with mean age, body mass index (BMI), and gender distribution targeted to be similar to the impaired hepatic function cohorts. Subjects will be confined to an inpatient facility from the evening before dosing to 144 hours after dosing.