lol Zithromax is an antibiotic (a macrolide more accordingly) too, so taking it because of a fear of your infection growing immune to penacillin are kind of...ironic. Not in the sense that they work exactly the same, but that it can grow immune to either just as well...

avoid aluminum magnesium (antacids contain this). It affects absorption into the blood stream.

plus side...it is used to treat some STDs, lol