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chapter 14 Nitrofurans and Fosfomycin 123
of less than 50 ml/min), there may be insufficient
accumulation of the drug in the urine for
activity. Nitrofurantoin in particular should be
avoided in these patients.
• Nitrofurantoin comes in two formulations: a
crystalline form (Macrodantin) and a macrocrystalline/monohydrate
form (Macrobid). The
former is dosed 4 times daily, the latter BID.
Guess which one patients prefer? Fosfomycin is
only available in the United States as a powder
that patients add to water before taking.
• A recent study of nitrofurantoin showed that it
can be used for five days instead of the traditional
seven-day regimen. This shorter regimen
may make nitrofurantoin therapy more palatable
for patients who are used to three-day
courses of other UTI drugs (TMP/SMX and
fluoroquinolones). Fosfomycin is used for an
even shorter duration: its approved regimen
for treatment of uncomplicated cystitis is a
single dose.
What It’s Good For
Treatment of uncomplicated cystitis in patients
with adequate renal function (for nitrofurantoin
and fosfomycin) and prophylaxis against recurrent
uncomplicated lower UTI (for nitrofurantoin).
Don’t Forget!
To repeat: do not use these drugs in anything but
uncomplicated cystitis. Nitrofurantoin or fosfomycin
use in pyelonephritis or urosepsis is a treatment
failure waiting to happen.