Nitrofurantoin (UTI in Pregnancy)

How it works

It is concentrated in urine and reduced by bacterial enzymes to reactive intermediates that damage bacterial DNA, ribosomal proteins and other macromolecules, giving activity against common urinary pathogens.

Prescribing in practice

• Avoid at term (around the time of delivery) because of the risk of neonatal haemolysis, and avoid in known glucose-6-phosphate dehydrogenase deficiency.
• It is ineffective in pyelonephritis as it does not achieve adequate tissue concentrations, and works only when renal function is adequate to concentrate it in urine.
• Counsel that it may turn the urine dark yellow or brown, and that nausea is common.

Monitoring

Routine monitoring is not required for short courses; reserve longer-term use for specialist settings where pulmonary and hepatic effects are watched for.

Counselling the patient

• Take with food to reduce stomach upset and complete the full course.
• The medicine may darken your urine, which is harmless.
• Tell your midwife or doctor how far along you are, as it is avoided close to delivery.

Evidence & guidelines

Nitrofurantoin is recommended as a first-line option for urinary tract infection in pregnancy in NICE and Public Health antimicrobial guidance, with avoidance near term.