Nitrofurantoin Drug Profile

What is Nitrofurantoin?

Nitrofurantoin is an antibiotic medication that belongs to the nitrofuran class of antimicrobial agents. It is primarily used to treat and prevent urinary tract infections (UTIs) caused by susceptible bacteria. This medication is particularly effective against common UTI-causing organisms and is often prescribed for uncomplicated bladder infections.

Uses

Nitrofurantoin has several approved medical uses:

• Acute uncomplicated cystitis: Treatment of bladder infections in women and men, particularly those caused by E. coli and other susceptible bacteria
• UTI prevention: Long-term prophylaxis for patients with recurrent urinary tract infections, especially in women with frequent episodes
• Acute pyelonephritis: Treatment of kidney infections when caused by susceptible organisms, though other antibiotics are often preferred
• Asymptomatic bacteriuria: Treatment in pregnant women when bacteria are present in urine without symptoms
• Chronic suppressive therapy: Prevention of UTIs in patients with structural urinary tract abnormalities or those at high risk for recurrent infections

How it works

Nitrofurantoin works by interfering with bacterial cell metabolism and DNA synthesis. The drug is activated by bacterial enzymes and then damages multiple cellular targets, including DNA, RNA, and essential metabolic pathways. This broad mechanism of action makes it effective against many gram-positive and gram-negative bacteria while making resistance development less likely.

Side effects

Common side effects include:

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• Nausea and vomiting
• Loss of appetite
• Diarrhea or loose stools
• Headache
• Dizziness
• Drowsiness
• Brown discoloration of urine
• Flatulence and abdominal pain

Serious side effects to watch for:

• Pulmonary toxicity (lung inflammation or scarring)
• Peripheral neuropathy (nerve damage in hands and feet)
• Liver toxicity or hepatitis
• Severe allergic reactions
• Blood disorders affecting white or red blood cells

Warnings and precautions

• Kidney function: Should be avoided in patients with severe kidney disease (creatinine clearance less than 30 mL/min) as the drug may not reach effective concentrations in urine and toxicity risk increases
• Pregnancy considerations: Generally considered safe in early pregnancy but should be avoided near term (38-42 weeks) due to risk of hemolytic anemia in newborns
• Lung disease monitoring: Patients should be monitored for signs of pulmonary toxicity, especially during long-term use, as this can be severe and sometimes irreversible
• Diabetes patients: May cause false-positive results in some urine glucose tests
• G6PD deficiency: Should be used with caution in patients with glucose-6-phosphate dehydrogenase deficiency due to increased risk of hemolytic anemia

Interactions

• Magnesium-containing antacids: Can reduce nitrofurantoin absorption; separate doses by 2-3 hours
• Probenecid: Increases nitrofurantoin blood levels and may reduce its effectiveness in treating UTIs while increasing toxicity risk
• Quinolone antibiotics: Nitrofurantoin may antagonize the antibacterial effects of fluoroquinolones
• Live typhoid vaccine: Nitrofurantoin may reduce vaccine effectiveness; avoid concurrent use
• Oral contraceptives: May rarely reduce contraceptive effectiveness; additional contraceptive methods may be advisable
• Warfarin: May enhance anticoagulant effects; monitor INR more frequently
• Methemoglobinemia-inducing drugs: Increased risk of methemoglobinemia when combined with other oxidizing agents
• Uricosuric agents: May reduce nitrofurantoin elimination and increase toxicity risk

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Dosage

Adult dosages vary based on the condition being treated and formulation used. For acute cystitis, the typical dose is 50-100 mg taken four times daily for 7 days, or 100 mg twice daily for modified-release formulations. For UTI prevention, long-term suppressive therapy typically involves 50-100 mg taken once daily at bedtime. The medication should be taken with food to improve absorption and reduce stomach upset. Dosages must always be determined by a healthcare provider based on individual patient factors, kidney function, and specific clinical circumstances.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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