Zithromax contains the active ingredient Azithromycin, which is a type of medicine known as a macrolide antibiotic. It is used to treat infections caused by bacteria.
Azithromycin works by preventing bacteria from producing proteins that are essential to them. Without these proteins the bacteria cannot grow, replicate and increase in numbers. Azithromycin therefore stops the spread of infection and remaining bacteria are killed by the body's immune system or eventually die.