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.