Roxithromycin: review of its antimicrobial activity.

Roxithromycin is a semi-synthetic 14-membered-ring macrolide antibiotic in which the erythronolide A lactone ring has been altered to prevent inactivation in the gastric milieu. The in-vitro activity of roxithromycin is well documented and similar to that of other macrolide antibiotics. Roxithromycin is active against gram-positive and gram-negative cocci, gram-positive bacilli and some gram-negative bacilli, but has no significant effect on the predominant faecal flora. It also displays good activity against atypical pathogens, such as Mycobacterium avium complex, Helicobacter pylori and Borrelia spp. It penetrates and accumulates within cells, such as macrophages and polymorphonuclear neutrophils (PMNs), where it is distributed between the cytosol and cellular granules. Once inside the cells, it is active against intracellular pathogens, such as Legionella, Chlamydia, Mycobacterium, Rickettsia and Borrelia spp. Like other macrolides, roxithromycin displays a significant post-antibiotic effect which is dependent on the pathogens under study, the concentration of roxithromycin and the duration of exposure. In vivo, roxithromycin is as effective or more effective than other macrolides in a wide range of infections.