First-lineMacrobid
Nitrofurantoin
Nitrofuran antibiotic
First-line UTI in T1/T2; avoid at term.
Oral
First-line for
- Lower UTI / asymptomatic bacteriuria in pregnancy
Mechanism
Reduced by bacterial nitroreductase → reactive intermediates damage DNA/ribosomes.
Nitro avoid: 'last weeks + G6PD'
- Avoid ≥36/40 — neonatal haemolysis
- Avoid G6PD deficiency
- Avoid eGFR <45
Dosing
- UTI
- 100 mg MR PO BD ×7 days (or 50 mg QDS)
Contraindications
- AbsoluteTerm (≥36/40) / labour / neonate <3 mo
- AbsoluteG6PD deficiency, eGFR <45
Side effects
- Nausea, brown urine
- Pulmonary fibrosis / hepatitis (chronic use)
- Peripheral neuropathy
Fetal & maternal notes
- • Safe T1/T2; risk of haemolytic anaemia if used at delivery.
Key interactions
Antacids (Mg)
Caution↓ absorption
Quinolones
CautionAntagonism
Clinical pearls
- 💡 Not for pyelonephritis (poor tissue levels).
- 💡 Trimethoprim alternative — avoid T1.
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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