Azithromycin is effective against Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Streptococcus pyogenes, Chlamydia trachomatis, Staphylococcus aureus, Mycoplasma pneumoniae, and Chlamydophila psittaci along with many other bacteria. It is not effective against viruses. It is more effective against gram-negative bacteria than other macrolides. Azithromycin can be administered once daily, because it has a long elimination half-life. After absorption, it stays in high concentrations in some specific types of cells, such as leucocytes, monocytes, and macrophages.
It has been shown that a once-a-day administration of azithromycin lasting for three days can have the same effectiveness as a once-a-day administration of other antibacterial agents that lasts for 5 or even 10 days. Side effects of azithromycin are mainly gastrointestinal in nature and occur in less frequency than other macrolides. It has lesser drug-drug interaction than other macrolides. Shorter duration of therapy, easy administration, and lesser adverse effect also account for the better compliance of patients towards azithromycin. It is helpful for patients who cannot take erythromycin due to several contraindications. (Dunn and Barradell, 1996). Read more http://lifespanmeds.com/zithromax.html .