Medication Name

Nitrofurantoin

General Description

Nitrofurantoin is an antibiotic specifically used to treat bladder infections. It is categorized under nitrofuran derivatives. Its prevalent forms include capsules, tablets, and liquid suspension. This medication works primarily by interfering with bacterial enzyme activities, which inhibits bacterial cell walls and prevents bacterial replication.

Formulations Available

Nitrofurantoin is available in several formulations, including immediate-release tablets, extended-release capsules, and liquid suspensions. Immediate-release tablets usually come in 50 mg and 100 mg strengths. Extended-release capsules are often found in strengths of 75 mg and 100 mg. The liquid suspension form is typically offered in a concentration of 25 mg/5 mL.

Mechanism of Action

Nitrofurantoin works by damaging bacterial DNA. Its active metabolite concentrates in the urine, where it exerts bactericidal effects. This process occurs as the drug interferes with bacterial carbohydrate metabolism, leading to structural damage within bacterial cells. Consequently, this prevents the growth and proliferation of the bacteria causing the urinary tract infection.

Indications for Use

This medication is primarily indicated for uncomplicated urinary tract infections caused by susceptible strains of Escherichia coli, Enterococcus, Staphylococcus aureus, and certain species of Klebsiella and Enterobacter. It is not intended for treating kidney infections or pyelonephritis. Additionally, it’s often prescribed for prophylaxis against recurrent urinary tract infections in certain patients.

Administration Instructions

Nitrofurantoin should be taken with food to enhance absorption and minimize gastrointestinal discomfort. Immediate-release forms are generally taken four times a day, while extended-release capsules are taken twice daily. Liquid suspensions should be measured accurately with a dosing spoon or syringe. Patients must complete the prescribed course, even if they feel better before it is fully consumed.

Dosage Recommendations

The typical adult dosage for uncomplicated urinary tract infections is 50 to 100 mg four times a day for a period of 7 days using immediate-release tablets. For extended-release capsules, the dosage is commonly 100 mg twice daily. In pediatric patients older than one month, the dosage is generally 5-7 mg/kg/day, divided into four doses for the immediate-release formulation.

Pediatric Usage

Nitrofurantoin is approved for pediatric use in children older than one month. Dosage in this age group should be carefully calculated based on body weight. The liquid suspension is often preferred as it allows for more precise dosing. Pediatric patients should be monitored for potential side effects such as gastrointestinal disturbances.

Geriatric Considerations

Elderly patients may have renal impairment, which could affect the excretion of Nitrofurantoin. Dosage adjustments might be necessary in this age group to avoid accumulation and toxicity. Renal function tests are recommended prior to initiating therapy to ensure appropriate dosing. Additionally, close monitoring during treatment is essential to identify any emerging adverse effects.

Pharmacokinetic Properties

Nitrofurantoin is rapidly and almost completely absorbed from the gastrointestinal tract, especially when taken with food. The serum half-life is relatively short, around 20 minutes, necessitating multiple daily doses for immediate-release formulations. It is extensively metabolized in the liver and the kidneys, and eventually excreted in the urine, where it reaches therapeutic concentrations.

Side Effects Experienced

The most common side effects include nausea, vomiting, and diarrhea. Less frequent effects can involve pulmonary reactions like interstitial pneumonitis and chronic pulmonary fibrosis, especially with long-term use. Peripheral neuropathy has been reported rarely, usually in patients with impaired kidney function.

Drug Interactions

Antacids containing magnesium trisilicate can reduce the absorption of Nitrofurantoin, thus diminishing its effectiveness. Concomitant use with probenecid can inhibit the renal excretion of Nitrofurantoin, leading to toxic serum levels. Certain quinolones may antagonize the antibacterial effect of Nitrofurantoin and should be avoided if possible.

Renal Impairment Considerations

Nitrofurantoin should not be used in patients with significant renal impairment, defined as a creatinine clearance less than 60 mL/min. Impaired renal function can lead to decreased elimination and increased risk of toxicity. Renal function should be assessed before initiating treatment, and alternative antibiotics should be considered if renal impairment is present.

Hepatic Impairment Concerns

Hepatic impairment does not significantly affect the pharmacokinetics of Nitrofurantoin. However, caution should still be exercised as liver function may indirectly affect drug metabolism. Liver enzymes should be monitored periodically during prolonged therapy to detect any potential hepatotoxicity early.

Pregnancy and Lactation

Nitrofurantoin is generally considered safe for use during pregnancy, except near term, as it can cause hemolytic anemia in the newborn. It can be used during breastfeeding but with caution, as small amounts are excreted in breast milk. Monitoring the infant for signs of gastrointestinal upset or allergic reactions is advised.

Missed Dose Protocol

If a dose of Nitrofurantoin is missed, it should be taken as soon as remembered unless it is almost time for the next dose. In such cases, the missed dose should be skipped, and the patient should continue with the regular dosing schedule. Doubling up on doses to make up for a missed one is not advisable.

Overdose Management

In case of overdose, supportive and symptomatic treatment should be provided. Inducing emesis or performing gastric lavage might be considered in recent ingestions. Monitoring the patient for signs of gastrointestinal distress, hepatic dysfunction, and neuropathy is essential in managing an overdose situation.

Patient Counseling Points

Patients should be advised to take Nitrofurantoin with food to enhance absorption and reduce gastrointestinal side effects. They should complete the entire course of therapy even if symptoms improve early to prevent resistance. Inform them about the potential for urine discoloration to a brownish color, which is harmless and expected.

Storage Recommendations

Nitrofurantoin formulations should be stored at room temperature, away from light and moisture. Immediate-release tablets and capsules should be kept in their original containers to protect from moisture. The liquid suspension should be shaken well before each use and stored in a tightly closed container. Ensuring proper storage is crucial to maintain the drug’s efficacy.