A Study of ABT-378/Ritonavir Combination in HIV-Infected Patients Who Have Taken Protease Inhibitors

Inclusion Criteria Concurrent Medication: Allowed: \- Antiretroviral regimen containing a protease inhibitor and one or two nucleoside reverse transcriptase inhibitors that has not changed in the last 12 weeks. Patients must have: \- HIV infection with plasma HIV RNA of at least 1,000 copies/ml and less than or equal to 100,000 copies/ml at screening. Prior Medication: Allowed: Naive to or has had less than 8 weeks of at least one nucleoside reverse transcriptase inhibitor and an acceptable regimen of two nucleoside reverse transcriptase inhibitors. Exclusion Criteria Concurrent Medication: Excluded: * Medications that are contraindicated with ABT-378/ritonavir for the duration of the study, such as midazolam, triazolam, terfenadine, astemizole, cisapride, pimozide, ergotamine and dihydroergotamine. * Over-the-counter medicine or alcohol, without knowledge or permission of the investigator. Patients with the following prior conditions are excluded: * Evidence of acute illness determined by vital signs, physical examination, or laboratory results. * Clinically significant abnormal ECG results. * Positive test result for drug abuse with the exception of cannabis, unless the investigator anticipates cannabis use will interfere with compliance with the study. Prior Medication: Excluded: * Investigational drugs with the exception of Amprenavir within 28 days prior to the initiation of study dosing. * Treatment with a non-nucleoside reverse transcriptase inhibitor. * Treatment with a protease inhibitor different from the current protease inhibitor for more than 6 weeks prior to current regimen. * Treatment with more than one protease inhibitor concurrently. Risk Behavior: Excluded: * Active substance abuse, alcohol abuse, psychiatric illness. * Presumption, by investigator, of poor compliance to regimen.