Roxithromycin is a semisynthetic macrolide antibiotic. It is used to treat infections of the respiratory tract, urinary tract, and soft tissues. Roxithromycin is derived from erythromycin and has an almost identical structure. Roxithromycin is most effective against certain Gram-negative bacteria, particularly Legionella pneumophila. It is also currently being tested in clinical trials for the treatment of male pattern hair loss. It is taken by mouth.