levofloxacin + ethambutol + rifampin + azithromycin

This is a combination regimen consisting of four antibiotics—levofloxacin, ethambutol, rifampin, and azithromycin—used primarily for the treatment of nontuberculous mycobacterial (NTM) infections such as Mycobacterium avium complex (MAC) pulmonary disease. Each component has a distinct mechanism of action: - **Levofloxacin** is a fluoroquinolone that inhibits bacterial DNA gyrase and topoisomerase IV, interfering with DNA replication. - **Ethambutol** inhibits arabinosyl transferases involved in cell wall biosynthesis in mycobacteria. - **Rifampin** inhibits DNA-dependent RNA polymerase in susceptible organisms, suppressing RNA synthesis. - **Azithromycin** is a macrolide antibiotic that binds to the 50S ribosomal subunit to inhibit protein synthesis. This multidrug approach is used because MAC and other NTM are resistant to most single agents; using multiple drugs reduces the risk of resistance development. The regimen may be considered for patients with refractory or severe disease or when standard regimens fail or are not tolerated[1][8]. Levofloxacin may be substituted for other agents if intolerance occurs[6].