KEY POINTS
- Nitrofurantoin is an antibiotic used to treat or prevent urinary tract infections
- Is reduced by bacterial flavoproteins to reactive intermediates that inactivate or alter bacterial ribosomal proteins. This leads to inhibition of protein synthesis, aerobic energy metabolism, DNA, RNA and cell wall synthesis.
- Bactericidal in urine at therapeutic doses
- E. coli (the most common bacteria to cause UTI) resistance is typically not as bad as that of with E. coli and ciprofloxacin or sulfamethoxazole-trimethoprim (Bactrim, SMX/TMP). This means nitrofurantoin may be a good choice for empiric therapy (i.e., when sensitivity is not known), but lower UTI is diagnosed and E. coli is suspected.
- Is indicated for lower urinary tract infections (i.e., not for pyelonephritis) and is also not a good choice if concern for prostatitis is present
- Dosing depends on the product
- Furadantin and Macrodantin are dosed 50-100mg every 6 hours
- Macrobid is dosed 100mg twice daily
- Note: “BID” is in the name and it is twice daily
- Generally avoid use in CrCl < 30 mL/min or elderly (>65 years old)
- Note: 60 mL/min was the previous cut-off, see link below: updated Beers Criteria 2015
- Poor kidney function will mean lower urinary concentrations and higher risk for toxicity
- Is normally well tolerated, but repeated or long-term use has been associated with pulmonary toxicity
- Liver toxicity, optic neuritis, and peripheral neuropathy have been reported
RESOURCES
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- Nitrofurantoin Macrocrystals (Macrodantin) Package Insert
- Nitrofurantoin Monohydrate/Macrocrystals (Macrobid) Package Insert
- Nitrofurantoin Oral Suspension (Furadantin) Package Insert
- IDSA UTI Guidelines
- American Geriatrics Society 2015 Updated Beers Criteria For Potentially Inappropriate Medication Use in Older Adults
- Nitrofurantoin Systematic Review & Meta-Analysis (2015, JAC) [free]
- Nitrofurantoin Systematic Review & Meta-Analysis Focusing On Safety/Efficacy For UTI Prophylaxis (2016, CMI)
