Nitrofurantoin : Therapeutic uses, Dosage & Side Effects
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
- 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.
- 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.