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Nitrofurantoin Dosage

Applies to the following strength(s): macrocrystals 50 mg ; macrocrystals 100 mg ; macrocrystals 25 mg ; macrocrystals-monohydrate 100 mg ; 25 mg/5 mL ; macrocrystals

The information at is not a substitute for medical advice. Always consult your doctor or pharmacist.

Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Cystitis

Regular release: 50 to 100 mg orally 4 times a day for 1 week or for at least 3 days after urine sterility is obtained
Dual release: 100 mg orally twice a day for 7 days

Usual Adult Dose for Cystitis Prophylaxis

Regular release: 50 to 100 mg orally once a day at bedtime

Usual Pediatric Dose for Cystitis

Regular release:
1 month or older: 5 to 7 mg/kg/day (up to 400 mg/day) orally in 4 divided doses

Dual release:
Greater than 12 years: 100 mg orally twice a day for 7 days

Usual Pediatric Dose for Cystitis Prophylaxis

Regular release:
1 month or older: 1 to 2 mg/kg/day (up to 100 mg/day) orally in 1 to 2 divided doses

Renal Dose Adjustments

Nitrofurantoin is contraindicated in patients with anuria, oliguria, or significant renal insufficiency (CrCl less than 60 mL/min or significantly elevated creatinine), due to the risk of toxicity.

Liver Dose Adjustments

Nitrofurantoin undergoes hepatic elimination. A dosage reduction may be necessary for patients with hepatic dysfunction.


Due to the risk of hemolytic anemia, nitrofurantoin is contraindicated in infants less than 1 month of age and in pregnant patients at term (38 to 42 weeks gestation), during labor and delivery, or when onset of labor is imminent.

Nitrofurantoin is contraindicated in patients with a history of cholestatic jaundice/hepatic dysfunction associated with nitrofurantoin.

Hepatic reactions may develop insidiously and have included hepatitis, cholestatic jaundice, chronic active hepatitis, and hepatic necrosis. Fatalities have been reported. Nitrofurantoin should be discontinued if hepatitis occurs. Liver function should be monitored periodically during therapy.

Nitrofurantoin has been associated with severe pulmonary toxicity with both short and long-term therapy. If a pulmonary reaction develops, therapy should be discontinued and the patient evaluated. Chronic pulmonary reactions may develop insidiously and have included diffuse interstitial pneumonitis and/or pulmonary fibrosis and have generally occurred in patients taking nitrofurantoin for 6 months or more. Pulmonary function should be closely monitored in patients on chronic therapy.

Potentially severe or irreversible peripheral neuropathy has been reported. Fatalities have occurred. Renal impairment, anemia, diabetes, electrolyte imbalance, vitamin B deficiency, and debilitating disease may increase the risk of neuropathy. Monitoring is recommended for patients on long-term therapy.

Clostridium difficile associated diarrhea (CDAD) has been reported with almost all antibiotics and may potentially be life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea following nitrofurantoin therapy. Mild cases generally improve with discontinuation of the drug, while severe cases may require supportive therapy and treatment with an antimicrobial agent effective against C difficile. Hypertoxin producing strains of C difficile cause increased morbidity and mortality; these infections can be resistant to antimicrobial treatment and may necessitate colectomy.

Nitrofurantoin has induced hemolytic anemia in patients with glucose-6-phosphate dehydrogenase deficiency. The drug should be discontinued if hemolysis occurs.

A greater proportion of severe hepatic and pulmonary reactions have been reported in geriatric patients. Monitoring of renal function is recommended.

Because of the potential for pulmonary toxicity and the availability of safer antimicrobials, nitrofurantoin meets the Beers criteria as a medication that is potentially inappropriate for use in older adults.

Prescribing the dual release formulation in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is not likely to provide benefit to the patient and increases the risk of developing drug-resistant bacteria.


Usage of nitrofurantoin should be avoided in patients on dialysis.

Other Comments

Patients should be advised to take nitrofurantoin with food to improve tolerance and drug absorption. Patients should be advised to avoid missing doses and to complete the entire course of therapy.