URANTIN 100

Indications

• Acute uncomplicated cystitis
• Recurrent urinary tract infections
• Prophylaxis against urinary tract infections

Dosage

Children: Refer to the BNF for Children for specific dosing guidelines.

Adults: Refer to the BNF for specific dosing guidelines.

Mechanism of action

Nitrofurantoin exerts its antimicrobial effect by being reduced to reactive intermediates within bacterial cells, which then damage bacterial DNA, RNA, and proteins. This leads to a disruption of cellular metabolism and ultimately bacterial cell death. The drug is particularly effective against Escherichia coli and other uropathogens.

Pharmacodynamics

Nitrofurantoin demonstrates concentration-dependent activity against susceptible organisms. It has a broad spectrum of activity and is bactericidal at therapeutic concentrations. The drug's efficacy is related to its ability to achieve high concentrations in the urine, which is crucial for treating urinary tract infections.

Pharmacokinetics

Nitrofurantoin is rapidly absorbed after oral administration, with peak plasma concentrations occurring within 1-2 hours. It is metabolized in the liver and primarily excreted unchanged in the urine, allowing it to exert its antibacterial action at the site of infection. The half-life of nitrofurantoin is approximately 30 minutes to 1 hour. Adequate renal function is necessary for its effectiveness, as reduced renal clearance can lead to decreased drug levels in the urine.

Contra-indications

• Known hypersensitivity to nitrofurantoin or any of its components
• Severe renal impairment (creatinine clearance less than 60 mL/min)
• Pregnant women at term (38-42 weeks) due to risk of hemolytic anemia in the newborn

Adverse effects

• Nausea and vomiting
• Diarrhea
• Headache
• Dizziness
• Pulmonary toxicity (including acute and chronic pulmonary reactions)
• Hepatotoxicity
• Peripheral neuropathy
• Hemolytic anemia (especially in patients with G6PD deficiency)

Interactions

• Antacids containing magnesium trisilicate may decrease the absorption of nitrofurantoin
• Probenecid may increase serum concentrations of nitrofurantoin
• Nitrofurantoin may enhance the effect of oral anticoagulants, increasing the risk of bleeding

Precautions

• Use with caution in patients with renal impairment, hepatic dysfunction, or glucose-6-phosphate dehydrogenase deficiency
• Monitor for signs of pulmonary toxicity, especially in long-term therapy
• Discontinue if signs of peripheral neuropathy occur

Pregnancy

Nitrofurantoin is generally avoided in the third trimester due to the risk of neonatal hemolytic anemia. It is classified as category B, indicating that animal reproduction studies have not shown a risk to the fetus.

Breast-feeding

Nitrofurantoin is excreted in breast milk in small amounts. Caution is advised, especially in nursing infants with G6PD deficiency.

Storage

Store in a cool, dry place, below 25 degrees Celsius, and protect from light.

Formulations

• Capsules (50 mg, 100 mg)
• Oral suspension (25 mg/5 mL)