A Study on the Interaction Between Danoprevir/Ritonavir and Methadone

Inclusion Criteria:

- Male and female adults, 18 - 65 years of age, inclusive

- Subjects must be on a stable methadone maintenance regimen (20 to 120 mg/day) for the
treatment of opiate addiction for at least 30 days prior to screening and should be
on a stable dose for at least 14 days prior to Day -1

- Body weight >/= 50 kg

- Body mass index (BMI) 18.0 - 32.0 kg/m2

- Females of childbearing potential and males with female partners of childbearing
potential must agree to use 2 forms of non-hormonal contraception during the study
and for 90 days after the last study drug administration

Exclusion Criteria:

- Pregnant or lactating women and male partners of women who are pregnant or lactating

- Symptoms of methadone withdrawal at screening, on Day -2 or Day -1

- Inadequate venous access

- History or evidence of any clinically significant disease or disorder, except for
drug abuse or dependence

- Positive test for alcohol or drugs of abuse at screening and up to Day -2 (with the
exception of methadone)

- History (within 3 months of screening) of alcohol consumption exceeding 2 standard
drinks per day on average (1 standard drink = 10 grams of alcohol); alcohol
consumption will be prohibited during study confinement and for at least 48 hours
before screening, dosing and each scheduled visit

- Positive for hepatitis B, hepatitis C or HIV infection