This is a Phase 1, open-label, parallel-group, single-dose study of lofexidine in 8 adult subjects with ESRD maintained on hemodialysis (3 times per week) and 8 control subjects with normal renal function (creatinine [Cr] clearance >90 mL/min), recruited as 1:1 matches to each ESRD subject, matched for gender, age (±10 years), and body mass index (BMI) (±15%). Normal renal function and ESRD subjects will be confined to an inpatient facility from the day before dosing to 144 or 156 hours after dosing, respectively, for a total of 7 8 nights and 8-9 days of inpatient confinement.