Nitrofurantoin : Uses, Dosage, Side Effects, Interactions, & Contraindications

Nitrofurantoin : Therapeutic uses, Clinical uses, Indications, Dosage, Side Effects, Warnings, Interactions, Precautions, Contraindications & Brand names

Nitrofurantoin is a urinary antiseptic. It is used to treat urinary tract infections.
Dose : 25-100 mg
Route : Oral
Onset of action : ?
Plasma Half-life : 30-60 min.
Duration of action : ?
Bioavailability : 40%
Plasma protein binding : ?
Metabolism : Renal
Pregnancy risk category : B
Chemical formula : C8H6N4O5
IUPAC name : (E)-1-[(5-nitro-2-furyl)methylideneamino]imidazolidine-2,4-dione
Trade name : Furadantin, Trifuran, Macrobid, Macrodantin, Nitro Macro
Antibacterial spectrum : Nitrofurantoin inhibits many gram-negative bacteria but due to development of resistance, activity is now restricted largely to E. coli. Gram-positive cocci (for example, S. saprophyticus) are typically susceptible. Its activity is enhanced at lower pH.
Therapeutic uses : Nitrofurantoin is indicated for uncomplicated lower urinary tract infection oniy but it is infrequently used now.

  • Acute infections due to E. coli can be treated with 50-100 mg TDS, given for 5-10 days. These doses should not be used for > 2 weeks at a time.
  • Suppressive long-term treatment has been successful with 50 mg BD.
  • It is also employed for prophylaxis of urinary tract infection when catheterization or instrumentation of the lower urinary tract is performed .

Mechanism of action : Nitrofurantoin sensitive bacteria reduce the drug to a highly active intermediate that inhibits various enzymes and damages bacterial DNA. Susceptible bacteria appear to enzymatically reduce nitrofurantoin to generate reactive intermediates which damage DNA.
Side effects : Nitrofurantoin may cause following side effects :

  • Gastrointestinal intolerance – nausea, emesis, epigastric pain and diarrhoea.
  • Neurologic problems like eripheral neuritis with long-term use.
  • Interstitial pulmonary fibrosis with chronic use.
  • Acute pneumonitis, liver damage
  • Dermatologic : Alopecia (hair loss).
  • Allergic : Pruritus, urticaria.
  • Haemolytic anaemia is rare, except in patients with G-6-PD deficiency.
  • An acute reaction with chills, fever and leucopenia occurs occasionally.
  • Urine of patients taking nitrofurantoin turns dark brown on exposure to air

Drug Interactions

  • NitrofurantoinΧ Nalidixic acid : Antagonizes the bactericidal action of nalidixic acid.
  • NitrofurantoinΧ Uricosuric drugs (Probenecid, sulfinpyrazone) : Uricosuric drugs inhibits its tubular secretion and reduces the concentration attained in urine -may interfere with its urinary antiseptic action.
  • NitrofurantoinΧ Antacids containing magnesium trisilicate :  Reduce both the rate and extent of absorption of nitrofurantoin.


Before using this medication, tell your doctor or pharmacist

  • If you are allergic to it; or if you have any other allergies.
  • Your medical history.


  • Contraindicated in renal failure or significant renal impairment.
  • Contraindicated during pregnancy (women who are 38 weeks or more pregnant) and in neonates.
  • Contraindicated in patients with a previous history of cholestatic jaundice/hepatic dysfunction associated with nitrofurantoindrug.
  • Contraindicated in those patients with known hypersensitivity to drug.

For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.

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