rifabutin + atazanavir + ritonavir

Rifabutin + atazanavir + ritonavir is a combination regimen used primarily in the management of tuberculosis (TB) in patients co-infected with human immunodeficiency virus (HIV), particularly when antiretroviral therapy includes protease inhibitors. Rifabutin is an antibiotic from the rifamycin class that inhibits DNA-dependent RNA polymerase in Mycobacterium tuberculosis, thereby suppressing bacterial RNA synthesis and leading to cell death. Atazanavir is an HIV-1 protease inhibitor that prevents viral replication by inhibiting the cleavage of viral polyproteins, while ritonavir acts as a pharmacokinetic enhancer by inhibiting cytochrome P450 3A4 (CYP3A4), increasing plasma concentrations of atazanavir and other co-administered drugs. The combination requires careful dose adjustment due to significant drug-drug interactions; for example, rifabutin doses are typically reduced when administered with boosted protease inhibitors like atazanavir/ritonavir to avoid toxicity while maintaining efficacy[1][2][4]. This regimen is recommended for HIV-infected TB patients where standard rifampicin-based regimens are contraindicated due to interactions with antiretroviral therapy.