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By Hans P. Schlecht, MD, MSc, Assistant Professor of Medicine, Department of Medicine, Division of Infectious Diseases & HIV Medicine, Drexel University College of Medicine
Christopher Bruno, MD, Assistant Professor of Medicine, Division of infectious Diseases & HIV Medicine, Drexel University College of Medicine

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Patient Education

Nitrofurantoin is bactericidal; the exact mechanism is unknown.

Nitrofurantoin is available only for oral use.


After a single dose, serum drug levels are very low, but urine drug levels are therapeutic.


Nitrofurantoin is active against common uropathogens, such as

  • Escherichia coli

  • Staphylococcus saprophyticus

  • Enterococcus faecalis

E. faecium, including vancomycin-resistant strains, and Klebsiella and Enterobacter sp are less susceptible. Most strains of Proteus, Providencia, Morganella, Serratia, Acinetobacter, and Pseudomonas spp are resistant. There is no cross-resistance with other antibiotic classes.

Nitrofurantoin is used only for

  • Treatment or prophylaxis of uncomplicated UTI

In women with recurrent UTIs, it may decrease the number of episodes.


Contraindications to nitrofurantoin use include

  • Previous allergic reaction to it

  • Renal insufficiency (creatinine clearance < 60 L/min)

  • Age < 1 mo

Use During Pregnancy and Breastfeeding

Nitrofurantoin is in pregnancy category B (animal studies show no risk and human evidence is incomplete, or animal studies show risk but human studies do not). Nonetheless, nitrofurantoin is contraindicated at term and during labor or delivery because it interferes with immature enzyme systems in RBCs of neonates, damaging the cells and resulting in hemolytic anemia.

Nitrofurantoin enters breast milk and is contraindicated during the first month of breastfeeding.

Adverse Effects

Adverse effects include

  • GI disturbances

  • Pulmonary toxicity

  • Peripheral neuropathy

  • Hemolytic anemia

  • Hepatic toxicity

Common adverse effects are nausea and vomiting, which are less likely with the macrocrystalline form. Fever, rash, acute hypersensitivity pneumonitis (accompanied by fever and eosinophilia), and chronic progressive pulmonary interstitial fibrosis may occur. Paresthesias may result and may be followed by a severe ascending motor and sensory polyneuropathy if the drug is continued, especially in patients with renal failure. Leukopenia and hepatic toxicity (acute cholestatic or chronic active hepatitis) have been reported, and hemolytic anemia can occur in patients with G6PD deficiency and in infants < 1 mo. Chronic pulmonary and hepatic reactions occur when the drug is used for > 6 mo.