Nitrofurantoin Cnx Therapeutics (Nitrofurantoin)

Nitrofurantoin is indicated for urinary tract infections and related prophylactic use.

• Uncomplicated cystitis: eradicates susceptible bacteria to resolve acute bladder infection.
• Prophylaxis of recurrent urinary tract infections: reduces frequency of infection episodes in patients with a history of recurrence.
• Treatment of urinary tract infection caused by susceptible organisms: provides bactericidal activity to clear infection.

• Nitrofurantoin exerts its antibacterial effect by entering bacterial cells and inhibiting key enzymatic processes. It interferes with bacterial ribosomal protein synthesis and generates reactive nitro‑furanyl intermediates that damage bacterial DNA. The combined inhibition of essential enzymes and DNA damage leads to rapid bactericidal activity against susceptible Gram‑negative and some Gram‑positive uropathogens. These actions are concentration‑dependent and occur primarily in the urinary tract where the drug is concentrated after oral absorption.

Nitrofurantoin may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Nausea: mild stomach upset often occurring after the first doses.
• Loss of appetite: reduced desire to eat.
• Headache: transient mild headache.
• Diarrhea: loose stools that usually resolve spontaneously.
• Skin rash: mild erythematous rash.
• Metallic taste: temporary alteration in taste perception.

Serious or Rare Side Effects

• Pulmonary toxicity: interstitial lung disease or acute respiratory distress.
• Hepatic injury: hepatitis or liver enzyme elevation.
• Severe allergic reaction: anaphylaxis or angioedema.
• Hemolytic anemia: especially in patients with G6PD deficiency.
• Peripheral neuropathy: numbness or tingling in extremities.
• Stevens‑Johnson syndrome: severe skin blistering.

Before prescribing Nitrofurantoin, clinicians should consider several safety precautions to minimize risk.

• Renal function assessment: avoid use in patients with creatinine clearance below 60 mL/min.
• Pregnancy timing: contraindicated in late pregnancy (≥ 38 weeks) due to risk of neonatal hemolysis.
• G6PD deficiency: do not use in individuals with known glucose‑6‑phosphate dehydrogenase deficiency.
• Elderly patients: monitor for reduced renal clearance and increased susceptibility to side effects.
• Concomitant pulmonary disease: use with caution and observe for new respiratory symptoms.
• Store at below 25°C: keep in the original packaging, protect from moisture and heat.

Nitrofurantoin can interact with other medicines, affecting its absorption or increasing toxicity.

Major Interactions (Avoid)

• Antacids containing magnesium or aluminum: reduce nitrofurantoin absorption.
• Probenecid: increases nitrofurantoin plasma levels and risk of toxicity.
• Warfarin: may enhance anticoagulant effect and increase INR.

Moderate Interactions (Monitor Closely)

• NSAIDs: combined use may impair renal function.
• Diuretics: may increase nitrofurantoin concentration in urine.
• Oral contraceptives: possible reduction in contraceptive effectiveness.