Merck Manual

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Brian J. Werth

, PharmD, University of Washington School of Pharmacy

Last full review/revision May 2020
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Nitrofurantoin is available only for oral use.


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

Indications for Nitrofurantoin

Nitrofurantoin is active against common uropathogens, such as

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

Nitrofurantoin is used only for

In women with recurrent urinary tract infections, it may decrease the number of episodes.

Contraindications to Nitrofurantoin

Contraindications to nitrofurantoin use include

Use During Pregnancy and Breastfeeding

Animal reproduction studies with nitrofurantoin have not shown risk to the fetus. No adequate and well-controlled studies have been done in pregnant women, but nitrofurantoin is generally considered to be safe during all 3 trimesters of pregnancy. However, nitrofurantoin is contraindicated at term and during labor or delivery because it interferes with immature enzyme systems in red blood cells of neonates, damaging the cells, and may result in hemolytic anemia.

Nitrofurantoin enters breast milk and should be avoided if possible during the first month of breastfeeding to reduce the risk of hemolytic anemia, especially in infants with hyperbilirubinemia.

Adverse Effects of Nitrofurantoin

Adverse effects of nitrofurantoin include

  • Gastrointestinal 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 month of age.

Chronic pulmonary and hepatic reactions occur when the drug is used for > 6 months.

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