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Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral, as macrocrystals:
Macrodantin: 25 mg
Macrodantin: 50 mg, 100 mg [contains fd&c yellow #10 (quinoline yellow), fd&c yellow #6 (sunset yellow)]
Generic: 25 mg, 50 mg, 100 mg
Capsule, Oral, as monohydrate/macrocrystals:
Macrobid: 100 mg [contains brilliant blue fcf (fd&c blue #1), fd&c red #40, fd&c yellow #10 (quinoline yellow)]
Generic: 100 mg
Furadantin: 25 mg/5 mL (230 mL)
Generic: 25 mg/5 mL (230 mL, 240 mL)
Brand Names: U.S.
- Antibiotic, Miscellaneous
Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates that inactivate or alter bacterial ribosomal proteins leading to inhibition of protein synthesis, aerobic energy metabolism, DNA, RNA, and cell wall synthesis. Nitrofurantoin is bactericidal in urine at therapeutic doses. The broad-based nature of this mode of action may explain the lack of acquired bacterial resistance to nitrofurantoin, as the necessary multiple and simultaneous mutations of the target macromolecules would likely be lethal to the bacteria.
Well absorbed; macrocrystalline is absorbed more slowly due to slower dissolution (causes less GI distress)
Vd: 0.8 L/kg
Body tissues (except plasma) metabolize 60% of drug to inactive metabolites
Suspension: Urine (~40%) and feces (small amounts) as metabolites and unchanged drug
Macrocrystals: Urine (20% to 25% as unchanged drug)
20-60 minutes; prolonged with renal impairment
60% to 90%
Special Populations: Renal Function Impairment
Nitrofurantoin accumulates in serum.
Use: Labeled Indications
Urinary tract infections: For the treatment of urinary tract infections (UTIs) when caused by susceptible strains of Escherichia coli, enterococci, Staphylococcus aureus, and certain susceptible strains of Klebsiella and Enterobacter species.
Acute cystitis: Nitrofurantoin monohydrate/macrocrystals: Indicated only for the treatment of acute uncomplicated UTIs (acute cystitis) caused by susceptible strains of E. coli or Staphylococcus saprophyticus in patients ≥12 years of age.
Anuria, oliguria, or significant impairment of renal function (creatinine clearance [CrCl] <60 mL/minute or clinically significant elevated serum creatinine); previous history of cholestatic jaundice or hepatic dysfunction associated with prior nitrofurantoin use; hypersensitivity to drug or any component of the formulation.
Note: The manufacturer’s contraindication in patients with CrCl <60 mL/minute has been challenged in the literature; limited data suggest that an alternative creatinine clearance threshold may be considered (Oplinger, 2013).
Because of the possibility of hemolytic anemia caused by immature erythrocyte enzyme systems (glutathione instability), the drug is contraindicated in pregnant patients at term (38 to 42 weeks gestation), during labor and delivery, or when the onset of labor is imminent; also contraindicated in neonates younger than 1 month of age.
Furadantin, Macrodantin: Oral: 50-100 mg/dose every 6 hours; administer for 7 days or at least 3 days after obtaining sterile urine
Macrobid: Oral: 100 mg twice daily for 7 days
UTI prophylaxis (Furadantin, Macrodantin): Oral: 50-100 mg/dose at bedtime
Avoid use; alternative agents preferred. Refer to adult dosing
Children >1 month (Furadantin, Macrodantin): Oral: 5-7 mg/kg/day in divided doses every 6 hours (maximum: 400 mg daily). Administer for 7 days or at least 3 days after obtaining sterile urine.
Children >12 years (Macrobid): Oral: Refer to adult dosing.
UTI prophylaxis: Children >1 month (Furadantin, Macrodantin): Oral: 1-2 mg/kg/day in divided doses every 12-24 hours (maximum: 100 mg daily) (Red Book [AAP] 2012)
Dosing: Renal Impairment
CrCl ≥60 mL/minute: No dosage adjustment provided in manufacturer’s labeling.
CrCl <60 mL/minute: Use is contraindicated. Note: Although more evidence is needed, limited data suggest clinicians consider use in patients with CrCl ≥40 mL/minute when treatment is short term (≤1 week) for an uncomplicated UTI (Oplinger, 2013). The Beers Criteria recommends avoiding use in geriatric patients ≥65 years with a CrCl <30 mL/minute (Beers Criteria [AGS 2015]).
Dosing: Hepatic Impairment
No dosage adjustment provided in manufacturer’s labeling. Contraindicated in patients with a previous history of cholestatic jaundice or hepatic dysfunction associated with nitrofurantoin.
Administer with meals to improve absorption and decrease adverse effects; suspension may be mixed with water, milk, fruit juice, or infant formula. Shake suspension well before use.
Take with meals to improve absorption and decrease adverse effects.
Capsules: Store at controlled room temperature, 15°C to 30°C (59°F to 86°F). Dispense in a tight container using a child-resistant closure.
Oral suspension: Avoid exposure to strong light, which may darken the drug. It is stable when stored between 20°C and 25°C (68°F and 77°F). Protect from freezing. Dispense in glass amber bottles.
BCG (Intravesical): Antibiotics may diminish the therapeutic effect of BCG (Intravesical). Avoid combination
BCG Vaccine (Immunization): Antibiotics may diminish the therapeutic effect of BCG Vaccine (Immunization). Monitor therapy
Dapsone (Topical): May enhance the adverse/toxic effect of Methemoglobinemia Associated Agents. Monitor therapy
Eplerenone: Nitrofurantoin may enhance the hyperkalemic effect of Eplerenone. Monitor therapy
Magnesium Trisilicate: May decrease the serum concentration of Nitrofurantoin. Avoid combination
Nitric Oxide: May enhance the adverse/toxic effect of Methemoglobinemia Associated Agents. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when nitric oxide is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine. Monitor therapy
Norfloxacin: Nitrofurantoin may diminish the therapeutic effect of Norfloxacin. Avoid combination
Prilocaine: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Prilocaine. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when prilocaine is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine in infants receiving such agents. Monitor therapy
Probenecid: May increase the serum concentration of Nitrofurantoin. Monitor therapy
Sodium Nitrite: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Sodium Nitrite. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Monitor therapy
Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Consider therapy modification
Spironolactone: Nitrofurantoin may enhance the hyperkalemic effect of Spironolactone. Monitor therapy
Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Vaccination with live attenuated typhoid vaccine (Ty21a) should be avoided in patients being treated with systemic antibacterial agents. Use of this vaccine should be postponed until at least 3 days after cessation of antibacterial agents. Consider therapy modification
False-positive urine glucose (Benedict's and Fehling's methods); no false positives with enzymatic tests
Frequency not defined.
Cardiovascular: ECG changes (nonspecific ST/T wave changes, bundle branch block)
Central nervous system: Bulging fontanel (infants), chills, confusion, depression, dizziness, drowsiness, headache, malaise, numbness, paresthesia, peripheral neuropathy, pseudotumor cerebri, psychotic reaction, vertigo
Dermatologic: Alopecia, erythema multiforme, exfoliative dermatitis, pruritus, skin rash (eczematous, erythematous, maculopapular), Stevens-Johnson syndrome, urticaria
Endocrine & metabolic: Hyperphosphatemia
Gastrointestinal: Abdominal pain, anorexia, Clostridium difficile associated diarrhea, constipation, diarrhea, dyspepsia, flatulence, nausea, pancreatitis, pseudomembranous colitis, sialadenitis, vomiting
Genitourinary: Urine discoloration (brown)
Hematologic & oncologic: Agranulocytosis, aplastic anemia, eosinophilia, glucose-6-phosphate dehydrogenase deficiency anemia, granulocytopenia, hemoglobin decreased, hemolytic anemia, leukopenia, megaloblastic anemia, thrombocytopenia
Hepatic: Cholestatic jaundice, hepatitis, hepatic necrosis, increased serum transaminases
Hypersensitivity: Anaphylaxis, angioedema, hypersensitivity (including acute pulmonary hypersensitivity)
Infection: Superinfection (eg, Pseudomonas or Candida)
Neuromuscular & skeletal: Arthralgia, lupus-like syndrome, myalgia, weakness
Ophthalmic: Amblyopia, nystagmus, optic neuritis
Respiratory: Acute pulmonary reaction (symptoms include chills, chest pain, cough, dyspnea, fever, and eosinophilia), cough, cyanosis, dyspnea, pneumonitis, pulmonary fibrosis (with long-term use), pulmonary infiltration
Postmarketing and/or case reports (Limited to important or life-threatening): Hepatotoxicty (idiosyncratic) (Chalasani, 2014)
Concerns related to adverse effects:
• Hepatic reactions: Rare, but severe and sometimes fatal hepatic reactions (eg, cholestatic jaundice, hepatitis, hepatic necrosis) have been associated with use (onset may be insidious); discontinue immediately if hepatitis occurs. Monitor liver function tests periodically. Use is contraindicated in patients with a history of nitrofurantoin associated cholestatic jaundice or hepatic dysfunction.
• Optic neuritis: Postmarketing cases of optic neuritis have been reported.
• Peripheral neuropathy: Has been associated with peripheral neuropathy (rare); risk may be increased in patients with anemia, renal impairment (CrCl < 60mL/min), diabetes, vitamin B deficiency, debilitating disease, or electrolyte imbalance; use caution.
• Pulmonary toxicity: Acute, subacute, or chronic (usually after 6 months of therapy) pulmonary reactions (possibly fatal) have been observed; if these occur, discontinue therapy immediately. Monitor closely for malaise, dyspnea, cough, fever, radiologic evidence of diffuse interstitial pneumonitis or fibrosis.
• Superinfection: Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months postantibiotic treatment.
• Hemolytic anemia: Use caution in patients with G6PD deficiency; may be at increased risk for hemolytic anemia. Discontinue therapy if occurs.
• Renal impairment: Urinary nitrofurantoin concentrations are variable in patients with impaired renal function. The manufacturer contraindicates use in CrCl <60 mL/minute; however, limited data suggest clinicians may consider using a lower threshold of CrCl ≥40 mL/minute when treatment is short term (≤1 week) for an uncomplicated UTI (Oplinger, 2013).
Concurrent drug therapy issues:
• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.
• Sedatives: Effects may be potentiated when used with other sedative drugs or ethanol.
• Elderly: Use in the elderly, particularly females receiving long-term prophylaxis for recurrent UTIs, has also been associated with an increased risk of hepatic toxicity and peripheral neuropathy. Monitor closely for toxicities during use.
• Pediatric: Use is contraindicated in children <1 month of age (at increased risk for hemolytic anemia).
• Appropriate use: Pyelonephritis: Not indicated for the treatment of pyelonephritis or perinephric abscesses.
Signs of pulmonary reaction; signs of numbness or tingling of the extremities; CBC, periodic liver function tests, periodic renal function tests with long-term use
Pregnancy Risk Factor
B (contraindicated at term)
Adverse effects have not been observed in animal reproduction studies. Nitrofurantoin crosses the placenta (Perry, 1967) and maternal serum concentrations may be lower in pregnancy (Philipson, 1979). Current studies evaluating maternal use of nitrofurantoin during pregnancy and the development of birth defects have had mixed results (ACOG, 2011). An increased risk of neonatal jaundice was observed following maternal nitrofurantoin use during the last 30 days of pregnancy (Nordeng, 2013). Nitrofurantoin may be used to treat infections in pregnant women; use during the first trimester should be limited to situations where no alternative therapies are available. Prescriptions should be written when clinically appropriate and for the shortest effective duration for confirmed infections (ACOG, 2011). Nitrofurantoin is contraindicated in pregnant patients at term (38-42 weeks gestation), during labor and delivery, or when the onset of labor is imminent due to the possibility of hemolytic anemia in the neonate. Alternative antibiotics should be considered in pregnant women with G-6-PD deficiency (Nordeng, 2013).
• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience nausea, diarrhea, lack of appetite, flatulence, or urine discoloration. Have patient report immediately to prescriber signs of pancreatitis, vision changes, ophthalmalgia, involuntary eye movements, illogical thinking, severe headache, depression, skin discoloration, significant asthenia, signs of pseudomembranous colitis (rare), signs of pulmonary disorder (rare), signs of hepatic impairment, or signs of severe neuropathy (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.
More about nitrofurantoin
- Nitrofurantoin (AHFS Monograph)
- Nitrofurantoin Capsules (FDA)
- Nitrofurantoin Macrocrystals (FDA)
- Nitrofurantoin Oral Suspension (FDA)