• Steady state area under the concentration time curve (AUC) between 0 and 12 hours of zidovudine (ZDV)-MP, ZDV-TP, and dTTP in PBMCs from HIV and hepatitis C virus (HCV) coinfected patients before and after peginterferon alfa-2b with or without ribavirin [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  
• Systemic exposure (AUC over 0 to 12 hours) of nelfinavir before and after peginterferon alfa-2b with or without ribavirin in HIV and HCV coinfected patients [ Time Frame: Throughout study ] [ Designated as safety issue: No ]
  
• Effect of peginterferon alfa-2b with or without ribavirin in HCV RNA viral titers, alanine aminotransferase (ALT) levels, CD4+, and HIV-RNA viral titers in HIV and HCV coinfected patients [ Time Frame: Through Week 48 ] [ Designated as safety issue: No ]
  
• Effect of peginterferon alfa-2b with or without ribavirin on liver histology [ Time Frame: At Week 72 ] [ Designated as safety issue: No ]
  

An estimated 50,000 people in Puerto Rico are infected with HCV. HIV and HCV have similar routes of transmission, and HCV co-infection occurs in 8% to 23% of HIV infected patients. Researchers have shown that treatment for HCV with Rebetron (ribavirin plus interferon alfa-2b) significantly decreases HCV viral load without affecting HIV viral load. However, measurements of intracellular levels of the active forms of zidovudine (ZDV-MP and ZDV-TP) were not performed. Such measurements are needed to provide a more rational basis for dosing in HIV/HCV co-infected patients. This study will investigate the intracellular exposure to active ZDV metabolites prior to and after treatment with Rebetron or treatment with PEG-Intron (pegylated interferon) and ribavirin.

Participants in this study will remain on their usual antiretroviral regimen; no changes may be made to that regimen for the first 4 weeks of the study. Upon study entry, participants will have intracellular pharmacokinetic studies. During Week 2, participants will start either Rebetron or PEG-Intron plus ribavirin therapy, will have intracellular pharmacokinetic studies, and will undergo liver biopsy. Additional intracellular pharmacokinetic studies will be performed at Weeks 12 and 24. Rebetron or PEG-Intron plus ribavirin will be given for 48 weeks. A second liver biopsy will be performed 24 weeks after discontinuing Rebetron or PEG-Intron plus ribavirin therapy. Participants will be followed for 72 weeks.