Sinusitis is not a simple matter-- not a thing to simply be cured or
not by the right antibiotic (although it is sometimes that simple).
Bacteria grow in sinuses not draining correctly, and the question is
why they aren't? Anatomical problems, allergies, what? Then there is
the problem that chronic sinus infections cause their own damage, and
tend to be mixed infections with anaerobes and even fungi.
Finally, there is the problem that there are many things not known
about this area. For instance, I've seen two people on high dose IV
mega antibiotics for hospital infections, who were also as a side
effect "cured" of nearly life long "seasonal allergies" thereby.
Apparently. What was going on there? I dunno.
If one has to treat chronic sinusitis with antibiotics alone, it's
probably best to try a regime with clindamycin in it, to get the
anaerobes, and metronidazole so the clinda doesn't cause C. difficile
for the 6 weeks you're going to be taking it. After that, it's a
tossup what broad-spectrum antibiotics to try, except that they need to
cover H. flu and strep and perhaps staph. Macrolides are not going to
be helpful if you're already using clindamycin, so Biaxin and Zithromax
are not great ideas. Augmentin or a fluoroquinolone can be used.
Rifampin is also sometimes very helpful as adjunct in getting at deep
seated infections with lots of pus (as in sinuses).
Quite often the main thing, however, is to see the ENT people about
drainage, and the allergy people about desensitization.