Nitrofurantoin

Nitrofurantoin Overview

Nitrofurantoin is an antibiotic medication primarily prescribed for the treatment of uncomplicated urinary tract infections (UTIs) caused by susceptible strains of bacteria. It is not effective for the treatment of pyelonephritis or perinephric abscesses.

Pharmacological Classification

This medication belongs to the nitrofuran antimicrobial class and operates by inhibiting bacterial ribosomal proteins, as well as other macromolecules. This action leads to the interference with the bacteria’s carbohydrate metabolism and cell wall synthesis.

Available Dosage Forms

Nitrofurantoin is available in oral capsule and suspension forms. The capsules come in two forms: macrocrystals, which are slower to be absorbed and less likely to cause stomach upset, and monohydrate/macrocrystals, a combination that has characteristics of both rapid and slow absorption.

Dosing Instructions

Standard dosing of nitrofurantoin for adults typically ranges from 50 mg to 100 mg taken four times daily. The exact dose and frequency depend on the severity of the infection and patient-specific factors. Patients are advised to take doses with food to enhance drug absorption and minimize stomach upset.

Adjustment for Renal Impairment

Nitrofurantoin requires dosage adjustments or may even be contraindicated in patients with significant renal impairment. The drug is usually not recommended for those with a creatinine clearance of less than 60 mL/min due to the potential for subtherapeutic antibiotic levels and increased risk of toxicity.

Indications for Use

Indicated for the treatment of acute uncomplicated UTIs, nitrofurantoin is effective against Escherichia coli, Enterococci, Staphylococcus saprophyticus, and certain other strains of bacteria. It is also utilized for the prophylaxis of recurrent lower urinary tract infections.

Side Effect Profile

Common side effects of nitrofurantoin may include gastrointestinal disturbances such as nausea, vomiting, diarrhea, and loss of appetite. Other side effects can include headache, dizziness, drowsiness, and brown discoloration of the urine. Long-term use may lead to pulmonary fibrosis, hepatotoxicity, and peripheral neuropathy.

Potential Drug Interactions

Interactions that can affect the efficacy of nitrofurantoin include antacids containing magnesium trisilicate, which can decrease its absorption. Probenecid and sulfinpyrazone can both inhibit renal excretion leading to increased blood levels of nitrofurantoin. Concurrent use with quinolone antibiotics may also reduce the antimicrobial effectiveness of nitrofurantoin.

Concomitant Disease Considerations

Patients with glucose-6-phosphate dehydrogenase deficiency may be at increased risk for hemolytic anemia when taking nitrofurantoin. Caution is advised in individuals with anemia, diabetes mellitus, electrolyte imbalances, or vitamin B deficiency. Additionally, concerns have been raised regarding possible exacerbation of myasthenia gravis symptoms with nitrofurantoin usage.

Pregnancy and Lactation

Whilst not generally contraindicated in pregnancy, nitrofurantoin should not be used at the time of labor and delivery or when onset of labor is imminent due to the potential risk of hemolytic anemia in the newborn. Nitrofurantoin is excreted in breast milk and should be used with caution in breastfeeding mothers, as it can induce hemolysis in infants with suspected or known glucose-6-phosphate dehydrogenase deficiency.

Storage and Handling

Nitrofurantoin should be stored at room temperature, away from direct light, moisture, and heat. The drug should be kept in its original container and out of reach of children. If the medication is supplied in a suspension form, it should be shaken well before each use and usually does not need refrigeration unless specified by manufacturer guidance.

Monitoring and Follow-Up

Treatment with nitrofurantoin requires follow-up to assess the effectiveness of the antibiotic therapy. This may involve a repeat urine culture to ensure the infection is cleared. Additionally, baseline and periodic monitoring of lung, liver and renal function may be recommended for patients on long-term therapy.

Medication Disposal

Unused or expired nitrofurantoin should be disposed of properly, in accordance with local regulations. It should not be flushed down the toilet or poured into a drain. Many communities have medication take-back programs or instructions for safe disposal.