Azithromycin (Zithromax) is a semi-synthetic macrolide antibiotic chemically derived from erythromycin which is active against a wide range of gram positive and gram negative microorganisms. Azithromycin (Zithromax) inhibits bacterial protein synthesis and prevents the growth and spread of bacteria. It is used to treat infections of upper and lower respiratory organs (tonsillitis, otitis, sinusitis, pneumonia), urogenital infections (urethritis, prostatitis, cervicitis, adnexitis, caused by chlamydia, gonorrhea, primary syphilis), intestinal infections, stomach and duodenal ulcer.