Nitrofurantoin (CKD Contraindication)

How it works

It is concentrated in the urine, where it is reduced by bacterial enzymes to reactive intermediates that damage ribosomal proteins, DNA and other macromolecules, giving activity confined largely to the urinary tract.

Prescribing in practice

• Nitrofurantoin should be avoided when renal function is significantly impaired because inadequate urinary concentrations make it ineffective while systemic accumulation raises the risk of peripheral neuropathy and pulmonary toxicity; check eGFR before prescribing.
• It is contraindicated in infants in the first months of life and in G6PD deficiency owing to the risk of haemolysis.
• Long-term use carries risks of chronic pulmonary fibrosis and hepatotoxicity, so prolonged courses need review.

Monitoring

Check renal function before prescribing and, with extended use, monitor for pulmonary, hepatic and neurological adverse effects.

Counselling the patient

• Take with food to reduce stomach upset, and expect your urine may turn dark yellow or brown.
• Report new tingling or numbness, breathlessness or persistent cough.

Evidence & guidelines

Long clinical experience and current prescribing references define its efficacy in uncomplicated cystitis and the renal threshold below which it is no longer recommended, with the threshold periodically revised.