Safety Study of Once a Day ART and Opiate Substitute. (3OD)

Inclusion Criteria: Ages 18 years or older Previously documented diagnosis of HIV-1 infection: by antibody assay (enzyme immunoassay confirmed by western immunoblot); or positive HIV culture; or detectable plasma HIV-1-RNA levels by reverse transcriptase polymerase chain reaction (RT-PCR). Receiving stable opiate substitution (stable methadone level for ≥ 2 weeks prior to entry into the study) with methadone, levomethadone or buprenorphine Either: Antiretroviral (ARV) therapy-naïve(*) and with: CD4 counts < 351 cells/µL; and/or HIV-1 plasma levels >= 30,000 copies/mL (*)less than 3 months of ART for vertical transmission is considered as ARV therapy naïve. Or restarting ART after treatment discontinuation with no evidence of prior HIV virological failure (virological failure defined as 2 consecutive measurements 4 weeks apart with viral load of HIV RNA > 400 copies/mL while on ART) Or currently receiving stable ART therapy and with virological suppression (< 400 copies/mL), for at least 6 months and: suffering from adherence problems because of dosing of current ART; or suffering from side effects on the current recorded ART. Able to give informed consent In the opinion of the investigator is likely to be able to complete the study Exclusion Criteria: Need for antiretroviral therapy which is not according to protocol Pregnant or breastfeeding women Females of childbearing potential not willing to use a barrier method(s) of contraception during heterosexual intercourse during the duration of the study Contraindication to use of tenofovir DF 300 mg or another concomitant medication Known hypersensitivity to the active component or excipients Prior receipt of tenofovir Evidence of clinical, genotypic, or phenotypic resistance to any ARV History of virological failure while on previously recorded ART regimens (virological failure defined as 2 consecutive measurements 4 weeks apart with viral load of HIV RNA > 400 copies/mL) Acute, life-threatening infection or malignancy that needs systemic therapy Any clinical laboratory findings obtained during screening that could be a risk factor for the patient during the study: Grade 4 increase of any laboratory value Grade 3 (> 5-10 upper limit of normal [ULN] increase in transaminases) at the screening visit Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study requirements. Current use of medication that, in the investigator's opinion or sponsor's opinion, will interfere with the study medication Participation in other clinical trials More than three months of ART treatment for vertical transmission prophylaxis Current receipt of adefovir dipivoxil