200 mg po bid.
There is also extended dosing (200 mg po twice daily on days 1–5, then once daily on alternate days for days 7–25) which in one study was superior to vancomycin (PubMed)
Important side effects
Even though not absorbed, it can still cause a hypersensitivity reaction (PubMed).
Rants and Screeds
Currently (Dec 2017) a course is around three thousand dollars. Really. $3,000. Can you say price gouge?
Treatment of choice
C. difficile diarrhea. Equal cure rates to vancomycin, fewer relapses (PubMed). It is cidal and has a prolonged post antibiotic effect; the first is probably unimportant, the second probably not so much much.
Don't use for
Macrocyclic antibiotic; inhibits the bacterial RNA polymerase,