Amoxicillin Dosing for UTI in Pregnancy
For pregnant patients with uncomplicated UTI, prescribe amoxicillin 500 mg orally three times daily for 3-7 days, with mandatory follow-up urine culture 7 days after completing therapy to confirm cure. 1
Recommended Dosing Regimens
Standard Treatment:
- Amoxicillin 500 mg orally three times daily for 3 days is the evidence-based first-line regimen for symptomatic UTI in pregnancy 1
- For asymptomatic bacteriuria (≥10⁵ CFU/mL), a single 3 g dose of amoxicillin plus 1 g probenecid can be used, though cure rates are lower (57%) compared to multi-day therapy (67%) 2
- Treatment duration can be extended to 7 days for more severe infections or if clinical response is suboptimal 3, 1
Alternative Dosing:
- Amoxicillin-clavulanate 20-40 mg/kg per day in 3 divided doses for 7 days provides broader coverage when resistance is suspected 4
- During pregnancy, amoxicillin and cephalosporins may be used but carry a higher chance of therapeutic failure compared to other agents 3
Critical Pre-Treatment Requirements
Mandatory urine culture collection before initiating therapy in all pregnant patients to guide antibiotic selection and confirm susceptibility 3
- Screen for asymptomatic bacteriuria at least twice during pregnancy (early and in 3rd trimester) 3
- All cases of significant bacteriuria (≥10⁵ CFU/mL) require treatment during pregnancy 3
- Repeat urine culture 7 days after completing therapy to assess cure or failure 1
When Amoxicillin is NOT Appropriate
First-line alternatives should be prioritized over amoxicillin:
- Fosfomycin trometamol 3 g single dose or nitrofurantoin 100 mg every 6 hours for 5 days are preferred first-line agents for uncomplicated cystitis in pregnancy 3
- Cefuroxime or amoxicillin-clavulanate for 7 days are second-line options 3
- Plain amoxicillin has approximately 80% cure rates for single-dose therapy in pregnancy, which is suboptimal 1
Prophylaxis for Recurrent UTI in Pregnancy
For pregnant women with history of recurrent UTI:
- Cephalexin 250-500 mg as postcoital prophylaxis is highly effective, reducing UTI incidence from 130 infections over 7 months to a single infection during pregnancy 5
- Nitrofurantoin 100 mg postcoital (contraindicated after 37 weeks gestation) is an alternative 3, 5
- Postcoital prophylaxis with a single dose is strongly recommended for any pregnant woman with recurrent UTI history 5
Common Pitfalls to Avoid
Single-dose therapy limitations:
- Single-dose amoxicillin (3 g) plus probenecid provides only 57% cure rate versus 67% for 10-day therapy in pregnancy 2
- Single-dose regimens do not adequately prevent reinfection during pregnancy 2
- For resistant organisms, cure rates are similarly poor for both short (43%) and long (48%) regimens 2
In vitro susceptibility testing does not reliably predict clinical cure with single-dose amoxicillin therapy 2
Nitrofurantoin must be discontinued after 37 weeks gestation due to risk of hemolytic anemia in the newborn 3
Treatment Duration Algorithm
- Asymptomatic bacteriuria: Single dose possible but 3-7 days preferred 3, 1
- Symptomatic uncomplicated cystitis: 3 days minimum, extend to 7 days if needed 3, 1
- Complicated UTI or inadequate response: 7-14 days based on clinical improvement 4
- Always obtain follow-up culture 7 days post-treatment to document cure 1