Raltegravir is the first integrase inhibitor used in humans. It has been shown to be highly efficacious and well tolerated in phase III clinical trials in multidrug experienced human immunodeficiency virus(HIV)-infected patients, as well as initial therapy in untreated patients. Pharmacokinetic studies in healthy adult subjects indicate that the major mechanism of clearance of the drug is glucuronidation mediated by UGT1A1, with a minor contribution of renal excretion of unchanged parent compound. Unlike CYP-based metabolism, glucuronidation is generally found to be relatively unaffected by hepatic disease. A single dose pharmacokinetic study of raltegravir in patients with mild to moderate hepatic insufficiency (Steigbigel et al. 2008) found no clinically important effect on the drug pharmacokinetic profile, with no dosage adjustment being necessary. The liver safety and tolerability of boosted atazanavir (ATV/r) has been evaluated in human immunodeficiency virus and hepatitis C virus (HIV/HCV) coinfected patients with advanced liver disease (decompensated cirrhosis) (Hermida JM et al. 4th IAS: Sidney, 2007). Similar to Raltegravir, ATV is also mainly metabolized by conjugation through UGT1A1. There is an urgent need for potent and efficacious ARV drugs with a clean safety liver profile even in patients with severe liver disease. The investigators hypothesized that pharmacokinetics will not be altered in HIV/HCV patients with advanced (Child-Pugh grade C) cirrhosis or in those with no histologic liver damage.

Inclusion Criteria:

• Adults, clinically stable HIV/HCV coinfected patients on HAART with controlled viremia (<50 copies/ml) for at least 6 months. HAART will be based on a boosted protease inhibitor (lopinavir, fosamprenavir or darunavir). Hepatic Stability is defined by the absence of new events of descompensation (Child-Pugh score) in the previous six weeks with no data of progressive hepatic insufficiency.
• Liver biopsy performed during the previous year showing no liver damage (F0-F1 in the Metavir score) or by elastometry results ≤ 6 Kpa, to classify patients in group B.
• Liver cirrhosis guided by biopsy (F4 in the Metavir score) or elastometry: results ≥ 14 Kpa, to classify patients in group A.
• Body mass index (BMI) in the range of 19-35 kg/m2.

Exclusion Criteria:

• HBV surface antigen positive.
• Clinical demonstration of a new descompensation event in the previous 6 weeks.
• Alcohol abuse as an average daily consumption > 20g.
• Treatment with boosted atazanavir, saquinavir or indinavir.
• Concomitant treatment with phenytoin, phenobarbital and rifampinor other UGT1A1 inhibitors.
• Use of any investigational agents (other than ART on expanded access) within 90 days of randomization.
• Active or previous HCV treatment with Ribavirin and /or Peg-interferon if sustained virological response achieved.
• Women taking oral contraceptives
• Pregnancy and lactancy.