Azithromycin is an azalide, a subclass member of the macrolide class of antibiotics that is a derivative of erythromycin. Following oral administration azithromycin is rapidly adsorbed and distributed throughout the body. The mechanism of action of this antibiotic includes binding to the 50S large subunit of bacterial ribosomes, thus interfering with protein synthesis. Azithromycin is used as a broad spectrum antibiotic, although it has been shown to be effective with serious infections including pneumonia. Side effects include fever, skin rash, swelling and difficulty in breathing.