Azithromycin as effective as penicillin for early-stage syphilis...

We know that azithromycin (structure) is one of the world's best-selling  antibiotics. It is derived from erythromycin; however, it differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring, thus making the lactone ring 15-membered.  Azithromycin is being used to treat or prevent certain bacterial infections, most often those causing middle ear infections, tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, Typhoid, certain urinary tract infections and venereal diseases, such as non-gonococcal urethritis, chlamydia, gonorrhea and cervicitis. and sinusitis. In recent years it has primarily been used to prevent bacterial infections in infants and those with weaker immune systems.

Now researchers lead by Dr. Edward W. Hook, III of University of Alabama at Birmingham have come up with an interesting finding, i.e., antibiotic pills (azithromycin) are as effective as penicillin injections in curing early-stage syphilis in HIV-negative volunteers. 

Although long-acting penicillin delivered by injection is recommended as the preferred treatment for early syphilis, the authors note that this therapy has shortcomings, particularly in resource-limited settings. Penicillin injections can cause allergic reactions, and the drug must be refrigerated and administrated by trained personnel. The orally administered azithromycin may provide a good alternative for treating HIV-negative people with early-stage syphilis, the scientists conclude. They note that there is a potential for syphilis-causing bacteria to acquire resistance to macrolide drugs such as azithromycin and they recommend continued research into this possibility..

Ref : http://www.niaid.nih.gov/news/newsreleases/2010/Pages/syphilis.aspx