Products
Nitrofurantoin is commercially available in many countries in the form of 100 mg sustained-release capsules (Furadantin retard, Uvamin retard). It has been used medicinally since the early 1950s.
Structure and properties
Nitrofurantoin (C8H6N4O, Mr = 238.2 g/mol) exists as a yellow crystalline powder that is very sparingly soluble in water. It is a nitrated furan and hydantoin derivative. The name is a composition of nitro (NO2), furan and hydantoin. By using the macrocrystalline agent, absorption is delayed and central side effects occur less frequently.
Effects
Nitrofurantoin (ATC J01XE01) has bacteriostatic to bactericidal properties against major uropathogens. It is a prodrug that is reduced to reactive electrophilic substances by bacterial enzymes called nitroreductases. These damage macromolecules such as DNA, proteins and enzymes. Nitrofurantoin is excreted mainly by the kidneys and has a short half-life of 20 to 90 minutes. Plasma concentrations are low and antibacterial concentrations are reached only in urine.
Indications
Nitrofurantoin is approved in many countries for the treatment of acute and chronic urinary tract infections and is used particularly for cystitis in women. Another area of application is infection prophylaxis during diagnostic examinations or after surgical procedures on the urinary tract system.
Dosage
According to the SmPC. The capsules are taken during or immediately after a meal with sufficient liquid because this increases gastrointestinal tolerance. They may also be administered with milk. The usual dosage for acute cystitis is one capsule two to three times daily for 5 to 7 days. For longer treatment, the capsules are administered only once or twice a day at the most, and check-ups are required. These include checking lung function, liver function, kidney function, nerve function and blood count. Therefore, the German technical information recommends limiting the duration of therapy to a maximum of 6 months.
Contraindications
- Hypersensitivity
- Renal insufficiency (risk of accumulation)
- Pathological liver enzyme levels
- Glucose-6-phosphate dehydrogenase deficiency
- Pregnancy in the last trimester, because of the risk of hemolytic anemia in the newborn (see SmPC).
- Premature infants, newborns
- Oliguria or anuria
- Polyneuropathy
- Acute porphyria
- Pulmonary fibrosis
- Children <12 years
Full precautions can be found in the drug label.
Interactions
Drug-drug interactions have been described with magnesium– and aluminum-salt-based antacids, atropine, urinary alkalinizing and acidifying agents, probenecid, quinolone antibiotics, phenytoin, and oral contraceptives, among others (selection). Nitrofurantoin is both filtered and secreted at the kidney. Laboratory tests may be confounded by nitrofurantoin.
Adverse effects
The most common possible adverse effects include:
- Gastrointestinal disturbances: Loss of appetite, nausea, vomiting.
- Nervous system: dizziness, ataxia, nystagmus, headache.
- Allergy: drug fever, itching, urticaria, angioedema.
- Lung: allergic pulmonary edema, pleurisy, dyspnea, cough, chest pain.
Patients should be made aware that the drug may discolor urine yellow or brown. Nitrofurantoin may rarely and especially with prolonged therapy cause serious side effects such as lung disease, severe allergic reactions, liver disease, severe skin reactions, anemia and neuropathy. In vitro, nitrofurantoin is mutagenic. It should therefore be used for as short a time as possible.