Nitrofurantoin

Nitrofurantoin is an antibiotic that was developed specifically for the treatment of urinary tract infections. It concentrates in the urine and acts there against the most common pathogens that cause bladder infections.

The medication has been in use for over 60 years and still has low resistance rates. It is particularly suitable for women with recurrent urinary tract infections, as it can also be used for long-term prophylaxis.

Well-known brand names are Furadantin®, Nifurantin®, and generics.

Nitrofurantoin has a bactericidal effect through several mechanisms:

Mechanism of action: After uptake into the bacterial cell, nitrofurantoin is reduced to reactive intermediates that:

• Damage bacterial DNA
• Inhibit ribosomal proteins
• Disrupt cell wall synthesis

Special features:

• Urine-acidifying agents increase its effectiveness, urine-alkalizing agents reduce it
• Concentrates in the urinary tract
• Hardly any systemic effect
• Very low resistance rate

Spectrum of activity:

• E. coli (most common pathogen)
• Enterococci
• Staphylococcus saprophyticus
• Limited: Klebsiella, Enterobacter

Nitrofurantoin is suitable for:

• Uncomplicated acute urinary tract infections
• Recurrent urinary tract infections
• Long-term prophylaxis in case of frequent recurrences

Particularly suitable for:

• E. coli infections
• Women with several infections per year
• As an alternative if fosfomycin fails

Not suitable for:

• Pyelonephritis (systemic effect too weak)
• Renal insufficiency (eGFR <45 ml/min)
• Pregnancy in the last trimester
• Glucose-6-phosphate dehydrogenase deficiency

Acute urinary tract infection:

• 100 mg 2x daily for 5-7 days OR
• 50 mg 4x daily for 5-7 days

Macrocrystalline form (extended-release):

• 100 mg 2x daily (better tolerated)

Prophylaxis:

• 50-100 mg in the evening or after sexual intercourse

Available forms:

• Capsules 50 mg, 100 mg
• Extended-release capsules 100 mg (macrocrystals)
• Suspension for children

How to take:

• Take with a meal or directly afterward
• Taking it with food improves tolerability and absorption of the active ingredient
• Take with plenty of water

Duration of treatment:

• Acute infection: 5-7 days (take the full course!)
• Prophylaxis: Long-term use possible under medical supervision

Important:

• Drink plenty of fluids
• Complete the full course of treatment
• Do not chew extended-release forms

For prophylaxis: Take in the evening or after sexual intercourse (postcoital).

Nitrofurantoin must not be taken in case of:

• Renal insufficiency (eGFR <45 ml/min)
• Glucose-6-phosphate dehydrogenase (G6PD) deficiency
• Acute porphyria
• Pregnancy in the last trimester (risk of hemolysis in the newborn)
• Breastfeeding during the infant's first months of life

Use with caution in case of:

• Renal insufficiency with an eGFR of 45 ml/min or above
• Anemia, diabetes, vitamin B deficiency (risk of neuropathy)
• Lung diseases
• Long-term use (regular monitoring)

Common (1-10%):

• Nausea, vomiting
• Diarrhea
• Loss of appetite
• Headache

Uncommon:

• Allergic reactions
• Dark yellow/brown discoloration of the urine (harmless)
• Dizziness

Rare but serious (especially with long-term therapy):

• Pulmonary fibrosis (chronic use)
• Peripheral neuropathy (tingling, numbness)
• Liver problems
• Hemolysis in G6PD deficiency

With long-term prophylaxis: Regular monitoring of lung function, liver function tests, and neurological status.

Interactions:

• Antacids containing magnesium – reduced absorption
• Probenecid – increased nitrofurantoin levels
• Fluconazole – increased toxicity

Do not combine with:

• Nalidixic acid – antagonistic effect
• Fluoroquinolones – reduced effect

No effect on:

• Hormonal contraception