With all due respect to DR, a z-pack won't do much for a serious illness, either. azithromycin is a macrolide, a derivative of erythromycin, and is efficient as heck-take the pills for 3-5 days, the azithromycin attaches to the white blood cells and remains active in the body for ten days. Useful for lots of different bacteria. lots of different kinds of infections-skin, lungs, sinuses-but only in mild disease. Penicillin-Pen V-K, amoxicillin, augmentin-are more common choices for moderately severe disease, but you gotta carry more of them, and you gotta take them for ten days to 2 weeks. Gets bulky. But it is like the multitool debate-a tiny one is easier to carry, less expensive to acquire...and almost useless if you have any significant work to do. A Z-pack is the ideal antibiotic to carry-compact and inexpensive-unless you actually need an antibiotic. Penicillin drugs are also one of the therapeutic choices for anthrax, for those of us who anticipate a bio-warfare scenario.