Nitrofurantoin is a prescription antibacterial medication specifically indicated for the treatment and prophylaxis of uncomplicated urinary tract infections (UTIs) caused by susceptible strains of Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and certain strains of Klebsiella and Enterobacter species. It belongs to the nitrofuran antibiotic class and functions by damaging bacterial DNA and inhibiting vital enzymatic processes, leading to bacterial cell death. Its unique pharmacokinetic profile ensures high concentrations in the urine with minimal systemic absorption, making it a first-line choice for lower UTIs while preserving gut and systemic microbiota. It is not effective for systemic infections or pyelonephritis due to inadequate tissue penetration.

Features

• Active ingredient: Nitrofurantoin (available as macrocrystals or monohydrate/macrocrystal formulations)
• Drug class: Antibacterial; nitrofuran derivative
• Administration: Oral (capsule, tablet, or oral suspension)
• Available strengths: 50 mg, 100 mg capsules; 25 mg/5 mL suspension
• Mechanism of action: Disrupts bacterial DNA, RNA, and cell wall synthesis; inhibits acetylcoenzyme A and other bacterial enzymes
• Spectrum of activity: Primarily gram-positive and gram-negative uropathogens
• Brand examples: Macrobid®, Furadantin®, Macrodantin®

Benefits

• Highly effective against common uropathogens with a well-established resistance profile
• Targeted action within the urinary tract minimizes disruption to gut flora, reducing risk of secondary infections like C. difficile
• Suitable for both acute treatment and long-term prophylaxis in recurrent UTI patients
• Low systemic absorption reduces risk of widespread side effects compared to broad-spectrum antibiotics
• Available in multiple formulations allowing for tailored dosing based on patient age and renal function
• Cost-effective generic options widely available

Common use

Nitrofurantoin is primarily prescribed for the treatment of acute, uncomplicated cystitis and for the prophylaxis of recurrent urinary tract infections. It is specifically indicated for lower UTIs and is not appropriate for upper tract infections (e.g., pyelonephritis) or systemic bacterial infections due to its limited tissue penetration. Its use is generally reserved for non-pregnant, non-lactating adult patients with normal renal function (CrCl >60 mL/min). It is often selected when first-line agents like trimethoprim-sulfamethoxazole are contraindicated due to resistance or allergy.

Dosage and direction

For acute cystitis:

• Macrocrystal/monohydrate (e.g., Macrobid®): 100 mg orally twice daily for 5 days
• Nitrofurantoin macrocrystals (e.g., Macrodantin®): 50 to 100 mg orally four times daily for 7 days (or 3 days in select cases)

For prophylaxis of recurrent UTIs:

• 50 to 100 mg orally once daily at bedtime

Take with food or milk to enhance absorption and minimize gastrointestinal upset. Do not crush or chew capsules. Dosage must be adjusted in patients with renal impairment (avoid if CrCl <60 mL/min). Not recommended in patients under 12 years of age or in pregnant patients at term.

Precautions

• Use with caution in patients with renal impairment (contraindicated if CrCl <60 mL/min)
• Monitor for pulmonary reactions (acute, subacute, or chronic); discontinue if respiratory symptoms develop
• May cause hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency
• Peripheral neuropathy has been reported; risk increases with prolonged use, renal impairment, anemia, diabetes, or electrolyte imbalance
• Superinfections (e.g., fungal or bacterial) may occur
• Not recommended during pregnancy at term (38–42 weeks) or during labor and delivery due to risk of hemolytic anemia in neonates
• May cause dizziness; advise patients to avoid driving or operating machinery until response is known

Contraindications

• Known hypersensitivity to nitrofurantoin or other nitrofuran derivatives
• Anuria, oliguria, or significant renal impairment (CrCl <60 mL/min)
• Infants under one month of age (risk of hemolytic anemia)
• Pregnancy at term (38–42 weeks), during labor, or delivery
• History of cholestatic jaundice or hepatic dysfunction associated with prior nitrofurantoin use
• Patients with G6PD deficiency

Possible side effect

Common (≥1%):

• Nausea, vomiting, anorexia
• Diarrhea or abdominal pain
• Headache
• Dizziness

Less common:

• Pulmonary reactions (cough, dyspnea, interstitial pneumonitis)
• Peripheral neuropathy (numbness, tingling)
• Hypersensitivity reactions (rash, pruritus, urticaria)
• Hepatitis, cholestatic jaundice
• Hemolytic anemia (especially in G6PD deficiency)
• Clostridium difficile-associated diarrhea
• Benign intracranial hypertension

Drug interaction

• Antacids containing magnesium trisilicate may reduce absorption and efficacy
• Probenecid may inhibit renal excretion, increasing systemic levels and toxicity risk
• Uricosuric agents (e.g., sulfinpyrazone) may decrease nitrofurantoin efficacy
• Drugs with neurotoxic potential (e.g., some antiretrovirals, chemotherapy) may increase risk of peripheral neuropathy
• May cause false-positive urine glucose tests if using copper reduction methods

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose. Do not double the dose to make up for a missed one. Maintain regular intervals to ensure consistent urinary concentration.

Overdose

Symptoms may include nausea, vomiting, and gastrointestinal distress. No specific antidote exists; management is supportive and includes gastric lavage if recent ingestion. Hemodialysis is not effective due to low systemic absorption. Contact a poison control center or seek emergency medical attention immediately.

Storage

Store at room temperature (20–25°C/68–77°F) in a tightly closed container. Protect from light and moisture. Keep out of reach of children and pets. Do not use after the expiration date.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult a healthcare professional for diagnosis, treatment decisions, and personalized dosing. Do not initiate, adjust, or discontinue medication without professional guidance.

Reviews

Clinical consensus supports nitrofurantoin as a first-line agent for uncomplicated UTIs, with high efficacy and favorable safety profile when used appropriately. Patient reviews often note rapid symptom relief, though gastrointestinal side effects are frequently reported. Long-term prophylactic use is well-tolerated in many patients with recurrent infections.