Nitrofurantoin

1. Introduction

Nitrofurantoin is an antibiotic used primarily to treat and prevent urinary tract infections (UTIs). It is effective against many gram-negative and gram-positive bacteria. Nitrofurantoin works by damaging bacterial DNA, ultimately preventing bacterial growth and reproduction. It is particularly effective in uncomplicated UTIs but is not recommended for systemic infections.

2. Indications

  • Acute uncomplicated urinary tract infections (e.g., cystitis)
  • Prophylaxis of recurrent urinary tract infections

3. Dosage

Adults:

  • Acute UTIs: 50–100 mg every 6 hours for 5–7 days.
  • Prophylaxis of recurrent UTIs: 50–100 mg once daily at bedtime.

Children (>1 month):

  • Acute UTIs: 5–7 mg/kg/day in divided doses every 6 hours (maximum: 400 mg/day).
  • Prophylaxis: 1 mg/kg once daily at bedtime (maximum: 100 mg/day).

Elderly:

  • Dose adjustments may be required due to reduced renal function; avoid in patients with creatinine clearance (CrCl) <30 mL/min.

4. Administration

  • Take orally with food or milk to enhance absorption and reduce stomach upset.
  • Ensure adequate fluid intake during treatment to support kidney function.
  • Swallow capsules or tablets whole; do not crush or chew.

5. Forms Available

  • Capsules: 25 mg, 50 mg, 100 mg
  • Oral suspension: 25 mg/5 mL
  • Modified-release capsules: 100 mg

6. Side Effects

6.1 Common Side Effects:

  • Nausea
  • Vomiting
  • Loss of appetite
  • Diarrhoea

6.2 Less Common Side Effects:

  • Dizziness
  • Headache
  • Rash or pruritus

6.3 Rare but Serious Side Effects:

  • Pulmonary toxicity (acute or chronic pulmonary fibrosis, especially with prolonged use)
  • Peripheral neuropathy
  • Hepatotoxicity
  • Haemolytic anaemia in patients with G6PD deficiency

7. Warnings

  • Pulmonary Toxicity: Acute and chronic pulmonary reactions, such as fibrosis or interstitial pneumonitis, may occur, particularly with prolonged use.
  • Peripheral Neuropathy: Use cautiously in patients with diabetes or other conditions predisposing to neuropathy.
  • Renal Function: Avoid in patients with CrCl <30 mL/min due to reduced efficacy and increased risk of toxicity.

8. Precautions

  • Avoid prolonged use, particularly in elderly patients, due to the risk of serious adverse effects.
  • Use with caution in patients with hepatic impairment, as nitrofurantoin can cause hepatotoxicity.
  • Not effective for systemic or pyelonephritis infections; restrict use to uncomplicated lower UTIs.

9. Interactions

  • Probenecid and Sulfinpyrazone: Reduce renal excretion of nitrofurantoin, increasing toxicity.
  • Magnesium-based antacids: Reduce absorption of nitrofurantoin.
  • Fluoroquinolones: Antagonistic effect when combined; avoid concurrent use.

10. Monitoring Parameters

  • Monitor renal function before and during prolonged therapy, especially in elderly patients.
  • Assess for signs of pulmonary toxicity, such as coughing or shortness of breath.
  • Monitor liver function tests in long-term use or patients with pre-existing liver disease.

11. Use in Children

  • Safe for children >1 month of age for uncomplicated UTIs and prophylaxis, but doses should be carefully calculated based on weight.

12. Use in Pregnancy

  • Generally safe during pregnancy but should be avoided during the last trimester due to the risk of haemolytic anaemia in the neonate.

13. Use in Elderly

  • Use with caution in elderly patients due to an increased risk of renal impairment and adverse effects. Avoid in patients with CrCl <30 mL/min.

14. Use in Kidney Disease

  • Avoid in patients with CrCl <30 mL/min due to reduced efficacy and increased toxicity.

15. Use in Liver Disease

  • Use cautiously in patients with hepatic impairment, as hepatotoxicity is a rare but serious side effect.

16. Patient Counselling Points

  • Take Nitrofurantoin with food to enhance absorption and reduce stomach upset.
  • Complete the full course of therapy, even if symptoms improve, to prevent antibiotic resistance.
  • Avoid skipping doses, as this may reduce effectiveness.
  • Inform your doctor immediately if you experience difficulty breathing, persistent cough, numbness or tingling, or yellowing of the skin or eyes.
  • Do not use Nitrofurantoin for severe kidney infections or systemic infections.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
MacrobidAlvogen100 mg Modified-Release Capsule$30 (14 capsules)
MacrodantinAlvogen50 mg Capsule$25 (30 capsules)
Generic NitrofurantoinVarious100 mg Capsule$15 (30 capsules)

18. 15 FAQs (Frequently Asked Questions)

1. What is Nitrofurantoin used for?
Nitrofurantoin is used to treat and prevent uncomplicated urinary tract infections.

2. How does Nitrofurantoin work?
It inhibits bacterial DNA, RNA, and protein synthesis, ultimately killing the bacteria.

3. What is the usual dose of Nitrofurantoin?
The typical dose for acute UTIs is 50–100 mg four times daily for 5–7 days.

4. Can Nitrofurantoin be used during pregnancy?
Yes, but it should be avoided in the last trimester due to the risk of haemolytic anaemia in the baby.

5. Can Nitrofurantoin cause pulmonary side effects?
Yes, pulmonary toxicity, such as interstitial pneumonitis or pulmonary fibrosis, may occur with prolonged use.

6. Can children take Nitrofurantoin?
Yes, it is safe for children >1 month for UTIs, but the dose must be adjusted based on weight.

7. Can Nitrofurantoin be taken with food?
Yes, taking it with food enhances absorption and reduces stomach upset.

8. Can Nitrofurantoin be used for kidney infections?
No, it is not effective for pyelonephritis or systemic infections.

9. Does Nitrofurantoin cause diarrhoea?
Yes, diarrhoea is a possible side effect. Report severe or persistent diarrhoea to your doctor.

10. Can Nitrofurantoin cause numbness or tingling?
Yes, peripheral neuropathy is a rare side effect. Report these symptoms immediately.

11. Is Nitrofurantoin effective for recurrent UTIs?
Yes, it can be used as prophylaxis for recurrent UTIs.

12. Can Nitrofurantoin cause liver damage?
Hepatotoxicity is a rare but serious side effect. Monitor liver function in long-term use.

13. Can Nitrofurantoin be used in elderly patients?
Yes, but caution is advised due to the risk of renal impairment and adverse effects.

14. Does Nitrofurantoin interact with other medications?
Yes, it interacts with probenecid, sulfinpyrazone, and magnesium-based antacids.

15. Do I need a prescription for Nitrofurantoin?
Yes, Nitrofurantoin is a prescription-only medication.