Estimate The Effect Of Lersivirine On The Pharmacokinetics Of S- And R-Methadone

Inclusion Criteria: * Healthy male and/or female subjects (Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history except drug abuse), full physical examination, including blood pressure and pulse rate measurement, 12-lead ECG and clinical laboratory tests). * Body Mass Index (BMI) of 17.5 to 35.5 kg/m2; and a total body weight \>50 kg (110 lbs). * Receiving stable methadone maintenance treatment for at least 3 months (dose range 50-150 mg QD). Exclusion Criteria: * Subjects on therapy for Hepatitis B and/or Hepatitis C; Evidence of impaired liver function (ie, AST and/or ALT greater than 3 times the upper limit of normal, total bilirubin \>1.5 times the upper limit of normal, albumin \<3.5 g/dL). * 12-lead ECG demonstrating QTc \>450 msec for males and QTc \>470 msec for females or any other clinically significant abnormalities at screening.