Nitrofurantoin Activase Pharmaceuticals (Nitrofurantoin, Macrocrystalline)

Nitrofurantoin is indicated for infections of the urinary tract, where it acts against susceptible bacteria.

• Uncomplicated urinary tract infection: eliminates causative bacteria and relieves symptoms such as dysuria and frequency.
• Acute cystitis: provides rapid bacteriological cure and symptom resolution in women with bladder infection.
• Prophylaxis of recurrent urinary tract infection: reduces recurrence rates when used as a long‑term preventive regimen.

• Nitrofurantoin is reduced by bacterial flavoprotein enzymes to reactive nitro‑reduced intermediates. These intermediates bind to bacterial DNA, causing strand breakage and inhibition of nucleic acid synthesis, and also disrupt carbohydrate metabolism. The selective activation within bacterial cells leads to bactericidal activity concentrated in the urine, while sparing most human cells.

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

Common Side Effects

• Nausea: mild stomach upset occurring in many patients.
• Vomiting: occasional expulsion of stomach contents.
• Diarrhea: loose stools that may be transient.
• Loss of appetite: reduced desire to eat.
• Headache: mild to moderate head pain.
• Metallic taste: unusual taste sensation in the mouth.

Serious or Rare Side Effects

• Pulmonary toxicity: interstitial lung disease or acute respiratory distress.
• Hepatic dysfunction: elevated liver enzymes or hepatitis.
• Hemolytic anemia: especially in patients with G6PD deficiency.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Peripheral neuropathy: numbness or tingling in extremities.
• Eosinophilic pneumonia: rare inflammatory lung condition.

Before prescribing nitrofurantoin, clinicians should consider several safety precautions.

• Renal function assessment: avoid use in patients with creatinine clearance below 60 mL/min.
• Pregnancy: limit use to cases where benefits outweigh potential risks, as safety data are limited.
• G6PD deficiency: monitor for signs of hemolysis and avoid in known deficiency.
• Elderly patients: use caution and monitor for toxicity due to reduced renal clearance.
• Concomitant medications: review for potential interactions that may affect nitrofurantoin levels.
• Store at ambient temperature: keep below 25 °C in the original packaging, protected from moisture.

Nitrofurantoin can interact with other medicines, altering its effectiveness or safety.

Major Interactions (Avoid)

• Antacids containing magnesium or aluminum: significantly reduce nitrofurantoin absorption.
• Probenecid: increases nitrofurantoin plasma concentrations, raising risk of toxicity.

Moderate Interactions (Monitor Closely)

• Warfarin: may enhance anticoagulant effect, requiring INR monitoring.
• Fluoroquinolones: additive risk of tendonitis or tendon rupture.
• Diuretics: may affect renal clearance and urinary concentration of the drug.
• Oral contraceptives: possible reduction in contraceptive efficacy.
• Vitamin C supplements: high doses may lower urinary pH and reduce drug activity.