You may have heard of an antibiotic called Zithromax, but do not know what it is. What is Zithromax? Well, many doctors prescribe it to patients to help them treat almost any type of bacterial infection. For example, the drug can be taken to clear up an ear infection, pneumonia, bronchitis, sinusitis, tonsillitis or a skin infection. Some patients even take Zithromax to help them treat their acne. The drug works by preventing bacteria from growing, and it is available in various formats. You can buy it in powder form, have it administered via injection or purchase extended-release or regular tablets.