Pharmacokinetic Study of Two HIV Protease Inhibitors in Patients

Inclusion Criteria: * HIV-seropositive * Currently receiving atazanavir/ritonavir or lopinavir/ritonavir in combination with 2-3 nucleoside RT inhibitors or are antiretroviral treatment-naïve * If female, is not of childbearing potential or is of childbearing potential and agrees to use a barrier method of contraception throughout the study Exclusion Criteria: * HIV-1 RNA \> 400 copies/mL if currently receiving antiretroviral therapy * Concurrent use of CYP450 inhibitors or inducers * Concurrent use of P-glycoprotein substrates, inhibitors, or inducers * Concurrent use of medications known to interact with ritonavir or atazanavir * Presence of a chronic health condition deemed by the investigators to potentially impair lopinavir, ritonavir, or atazanavir pharmacokinetics * Presence of conduction abnormalities on electrocardiogram * Women who are pregnant or breastfeeding * Laboratory Abnormalities at baseline: * Aminotransferases \> 3x ULN * Serum bilirubin \> 5x ULN * Serum creatinine \> 1.5x ULN * Hemoglobin concentration \< 8.0 g/dL * Absolute neutrophil count \< 800 cells/μL * Platelet count \< 50,000 cells/μL