Zithromax is the trade name and belongs to the group of drugs called Azithromycin. This drug is an azalide antibiotic, a sub class of macrolides. It retains the spectrum of activity of erythromycin against Gram-Positive and Gram-Negative pathogens and has increased activity against many Gram-Negative and atypical micro organisms. It has greater acid stability than erythromycin and its gastro intestinal tolerance is better than that of erythromycin. Zithromax acts by interfering with microbial protein synthesis by binding to the 50 S ribosomal sub units. It is mainly used in upper and lower respiratory tract infections, skin & soft tissues infections and uro-genital infection.