1st and 2nd trimester –

First-line: Nitrofurantoin* oral 50mg 6 hourly

Second-line: Cefalexin oral 500mg 8 hourly

3rd trimester –

Cefalexin oral 500mg 8 hourly

Total course duration: 7 days.

• Culture prior to treatment.
• Treat asymptomatic bacteriuria in pregnancy.
• Re-culture 7 days after completion of course.
• Refer to BNF for information on the use of antibiotics in pregnancy.

*Nitrofurantoin:

• Contraindicated if eGFR <30ml/minute/1.73m² or G6PD deficiency.
• Use with caution if eGFR 30–44ml/minute/1.73m² when resistance to other agents is suspected.
• Nitrofurantoin MR 100mg twice daily oral formulation is available as a pre-pack for hospital discharge.