What antibiotic should be prescribed for a pregnant patient with a urinary tract infection (UTI) confirmed by positive urinalysis for nitrates and leukocyte esterase?

Treatment of Urinary Tract Infection in a Pregnant Patient with Preeclampsia

Nitrofurantoin is the most appropriate antibiotic for treating a UTI in this 27-year-old pregnant patient with preeclampsia who has dysuria, increased frequency, and positive urinalysis for nitrates and leukocyte esterase. 1, 2

Diagnostic Confirmation

• Positive urinalysis for nitrates and leukocyte esterase strongly suggests a urinary tract infection, especially in the presence of symptoms like dysuria and increased frequency 3, 1
• Obtaining a urine culture before initiating antibiotics is recommended to guide definitive therapy, though empiric treatment can be started while awaiting results 1

First-Line Treatment Options for UTI in Pregnancy

• Nitrofurantoin is recommended as first-line therapy for uncomplicated UTIs in pregnant women due to its effectiveness and safety profile during pregnancy 1, 2
• Nitrofurantoin achieves high urinary concentrations and has minimal systemic absorption, making it particularly suitable for lower urinary tract infections 2, 4
• The American Urological Association recommends nitrofurantoin as a preferred agent for treating UTIs in pregnant women 1

Why Nitrofurantoin is Preferred in This Case

• Nitrofurantoin has maintained low resistance rates against common uropathogens, making it effective for empiric therapy 2, 4
• It is safe to use during pregnancy, with minimal risk to the developing fetus when used appropriately 1, 2
• The standard dosing is nitrofurantoin 100 mg twice daily for 5-7 days for uncomplicated UTIs 1

Why Other Options Are Less Appropriate

• Ceftriaxone (option A) is overly broad-spectrum for an uncomplicated UTI and is typically reserved for pyelonephritis or more severe infections 3
• Cefazolin (option C) is primarily used for parenteral administration and would not be first-line for an uncomplicated UTI that can be treated orally 3
• Meropenem (option D) is a carbapenem antibiotic that should be reserved for multidrug-resistant infections and is not appropriate for first-line treatment of uncomplicated UTIs 3

Special Considerations for Pregnant Patients with UTI

• Pregnant women should be screened for bacteriuria at least once in early pregnancy due to increased risk of pyelonephritis 3
• Untreated bacteriuria in pregnancy can lead to pyelonephritis in 20-30% of cases, compared to 1-2% in treated patients 3
• Preeclampsia requires careful medication selection to avoid worsening maternal or fetal outcomes 1

Monitoring and Follow-up

• Clinical improvement should be expected within 48-72 hours of initiating appropriate therapy 1
• A follow-up urine culture after completing treatment is recommended to ensure eradication of the infection, especially in pregnancy 3, 1
• Patients should be monitored for potential adverse effects of nitrofurantoin, including pulmonary reactions, though these are rare with short-term use 5, 6

Potential Pitfalls and Caveats

• Nitrofurantoin should not be used in patients with significant renal impairment (creatinine clearance <60 mL/min) as it may not achieve adequate urinary concentrations and increases risk of toxicity 5
• Nitrofurantoin is not appropriate for suspected pyelonephritis as it does not achieve therapeutic blood concentrations 1, 7
• If symptoms worsen or do not improve within 48-72 hours, reassessment and alternative antibiotic therapy should be considered 1