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Urinary Antiseptic Antibiotic Pregnancy: §4.6: animal studies have shown no teratogenic effects, although a study in rats showed reproductive toxicity. Nitrofurantoin has been in extensive clinical use since 1952 and its suitability in human pregnancy has been well documented; the drug should be used at the lowest dose appropriate for the specific indication, only after careful assessment. It is contraindicated in pregnant women during labour and delivery (and in infants under three months of age) because of the possible risk of haemolysis of the infant's immature red cells. Breast-feeding an infant known or suspected to have an erythrocyte enzyme deficiency (including G6PD deficiency) must be temporarily avoided, since nitrofurantoin is detected in trace amounts in breast milk.

Nitrofurantoin (Paediatric — UTI Prophylaxis)

Brand names: Macrobid, Furadantin

Nitrofurantoin (paediatric — UTI prophylaxis) is a urinary antibacterial used in children to prevent recurrent lower urinary tract infections. This page covers its use for paediatric UTI prophylaxis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Acute uncomplicated urinary tract infection: 50 mg four times daily for seven days. Long term suppression: 50 to 100 mg once a day
Route: Oral — should always be taken with food or milk (taking nitrofurantoin with a meal improves absorption and is important for optimal efficacy)
Frequency: Four times daily for seven days (acute UTI); once a day (long term suppression)
Source: UK SPC (eMC) for Nitrofurantoin 100 mg Capsules, §4.2 (https://www.medicines.org.uk/emc/product/12565/smpc). No maximum dose is stated in §4.2. OTHER ADULT REGIMENS: severe chronic recurrence of UTI — 100 mg four times daily for seven days; prophylaxis — 50 mg four times daily for the duration of the procedure and for three days thereafter. ELDERLY: provided there is no significant renal impairment (in which nitrofurantoin is contraindicated), the dosage should be that for any normal adult; note the precautions and risks to elderly patients associated with long-term therapy. PAEDIATRIC POSOLOGY is captured in the paedDose block. FORMULATION NOTE: for children under the age of 6 years or under 25 kg body weight, consideration should be given to the use of nitrofurantoin oral suspension.

Paediatric dose

Dose: 1 mg/kg
Route: Oral (take with food or milk)
Frequency: Once a day (suppressive / prophylactic regimen — matches this page's indication)
Max: Not stated in §4.2
SPC §4.2, children and infants over three months of age: 'Suppressive - 1mg/kg, once a day.' The same section gives the treatment regimen for acute urinary tract infections as '3mg/kg day in four divided doses for seven days' — dosePerKg above reflects the SUPPRESSIVE/prophylactic regimen because that is this page's indication; use 3 mg/kg/day in four divided doses if treating an acute UTI. Nitrofurantoin is contraindicated in infants under three months of age (§4.3). For children under the age of 6 years or under 25 kg body weight, consideration should be given to the use of nitrofurantoin oral suspension. Verify all paediatric dosing against a children's formulary before prescribing.

Dose adjustments

Renal

Nitrofurantoin is contraindicated in patients with renal dysfunction and in patients with an eGFR of less than 45 ml/minute (§4.2/§4.3). §4.4 adds that it may be used with caution as short-course therapy only, for uncomplicated lower urinary tract infection in individual cases with an eGFR between 30 and 44 ml/min, to treat resistant pathogens when the benefits are expected to outweigh the risks.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

SPC §4.2, children and infants over three months of age: 'Suppressive - 1mg/kg, once a day.' The same section gives the treatment regimen for acute urinary tract infections as '3mg/kg day in four divided doses for seven days' — dosePerKg above reflects the SUPPRESSIVE/prophylactic regimen because that is this page's indication; use 3 mg/kg/day in four divided doses if treating an acute UTI. Nitrofurantoin is contraindicated in infants under three months of age (§4.3). For children under the age of 6 years or under 25 kg body weight, consideration should be given to the use of nitrofurantoin oral suspension. Verify all paediatric dosing against a children's formulary before prescribing.

Verify in a children's formulary

Contraindications

  • Hypersensitivity to the active substance, to other nitrofurans, or to any of the excipients
  • Renal dysfunction with an eGFR below 45 ml/minute
  • G6PD deficiency
  • Acute porphyria
  • Infants under three months of age, and pregnant patients at term (during labour and delivery), because of the theoretical possibility of haemolytic anaemia in the foetus or newborn infant due to immature erythrocyte enzyme systems

Side effects

  • Not known: acute, subacute and chronic pulmonary reactions (including pulmonary fibrosis and diffuse interstitial pneumonitis), cough, dyspnoea — discontinue immediately if these occur
  • Not known: chronic active hepatitis (fatalities have been reported), hepatic necrosis, autoimmune hepatitis, cholestatic jaundice
  • Not known: peripheral neuropathy including optic neuritis (sensory and motor involvement), which may become severe or irreversible — stop treatment at the first signs of neural involvement (paraesthesia); also nystagmus, vertigo, dizziness, headache, drowsiness and benign intracranial hypertension
  • Not known: nausea, anorexia, emesis, abdominal pain and diarrhoea; sialadenitis, pancreatitis
  • Rare: aplastic anaemia; not known: agranulocytosis, leucopenia, granulocytopenia, haemolytic anaemia, thrombocytopenia, megaloblastic anaemia and eosinophilia. Also allergic skin reactions, angioneurotic oedema and anaphylaxis; exfoliative dermatitis and erythema multiforme (including Stevens-Johnson syndrome), DRESS, cutaneous vasculitis; yellow or brown discolouration of urine; interstitial nephritis
  • NOTE: the §4.8 table was truncated at the source-fetch limit — this list is incomplete

Interactions

  • NOTE: §4.5 was not present in the fetched UK bundle — the entries below are from the US label and must be confirmed against the UK SPC
  • Antacids containing magnesium trisilicate — reduce both the rate and extent of nitrofurantoin absorption; if co-administration cannot be avoided, monitor for lack of efficacy (US label §7.1)
  • Uricosuric drugs such as probenecid and sulfinpyrazone — inhibit renal tubular secretion of nitrofurantoin; the resulting increase in serum levels may increase toxicity and the decreased urinary levels could lessen efficacy as a urinary tract antibacterial, so monitor for adverse reactions (US label §7.2)
  • Laboratory interference — nitrofurantoin can cause a false-positive reaction for glucose in urine with Benedict's or Fehling's copper reduction tests; use enzymatic glucose oxidase-based tests instead (US label §7.3; UK §4.4 also notes false positive urinary glucose)

Clinical monograph

How it works

It is reduced by bacterial enzymes to reactive intermediates that damage bacterial DNA, ribosomal proteins and other macromolecules, concentrating in the urine to act at the site of infection.

Prescribing in practice

  • The most important paediatric concern is that nitrofurantoin must be avoided in infants in the first few months of life and is contraindicated in significant renal impairment, where reduced urinary concentration cuts efficacy and the risk of toxicity rises, and it carries a risk of haemolysis in G6PD deficiency.
  • It treats lower urinary tract infection only and is not suitable for pyelonephritis or systemic infection because it does not reach adequate tissue concentrations.
  • Long-term prophylactic use requires periodic review for the rare risks of pulmonary and hepatic reactions; doses should be confirmed against a children's formulary.

Monitoring

Monitor for recurrence, and on prolonged prophylaxis review periodically for respiratory, hepatic and neurological adverse effects.

Counselling the patient

  • Give with food to improve absorption and reduce stomach upset.
  • The urine may turn yellow-brown, which is harmless.
  • Report any breathlessness, persistent cough, jaundice or numbness and tingling.

Evidence & guidelines

NICE guidance supports antibiotic prophylaxis, including nitrofurantoin, for selected children with recurrent urinary tract infection, with use avoided in young infants and renal impairment.

Reference: NICE NG224 UTI in Children; RIVUR Trial (Hoberman et al, NEJM 2014); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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