antibioticsbooks

chapter 13 Nitroimidazoles 119
• Metronidazole has excellent (~100%) bioavailability
and none of the drug-chelating concerns
of the fluoroquinolones; thus, patients should
be switched from IV to oral metronidazole as
soon as they are tolerating oral medications.
• Resistance to metronidazole among isolates of
C. difficile is uncommon, but treatment failure
with this infection is not. The organism can
exist as an antibiotic-resistant spore and cause
relapses after the end of treatment. Re-treatment
with metronidazole is reasonable in most cases
of mild or moderate relapsing C. difficile infection,
although treatment with oral vancomycin
or fidaxomicin is an alternative.
What They’re Good For
Infections with documented or suspected abdominal
anaerobic bacteria, with adjunctive coverage of
aerobes by a second drug when necessary. They are
also used for treatment of vaginal trichomoniasis
and GI infections caused by susceptible protozoa
(amebiasis, giardiasis, etc.). Metronidazole is also
a component of therapy for H. pylori GI ulcer disease
in combination with other antibacterials and
acid-suppressive drugs. It is also a drug of choice
for mild to moderate C. difficile infections.
Don’t Forget!
The GI flora of humans is a delicate ecosystem—
disturb it at your patient’s peril. Metronidazole’s
effect on the normal (primarily anaerobic) GI flora
can set up your patients for colonization with nasty
bugs such as VRE; determine whether you really
need anaerobic coverage.