First-Line Treatment for Urinary Tract Infection
For uncomplicated UTI in women, use nitrofurantoin (100 mg twice daily for 5 days), trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days), or fosfomycin (3g single dose) as first-line therapy, with selection based on your local antibiogram. 1, 2
Treatment Selection Algorithm
Step 1: Confirm Uncomplicated UTI
- Obtain urinalysis and urine culture before initiating treatment in patients with recurrent UTIs 1
- For first-time uncomplicated cystitis in otherwise healthy women, diagnosis can be made without an office visit or culture 3
- Exclude risk factors for complicated UTI (structural abnormalities, immunosuppression, pregnancy, male sex) 1
Step 2: Choose First-Line Agent Based on Local Resistance
Preferred first-line options:
- Nitrofurantoin: 100 mg twice daily for 5 days - has the lowest resistance rate (2.6% initially, 5.7% at 9 months) 2, 4
- Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 3 days - only if local E. coli resistance is <20% 1, 3
- Fosfomycin trometamol: 3g single dose - recommended specifically for women with uncomplicated cystitis 1, 2
Step 3: Avoid Common Pitfalls
Do NOT use fluoroquinolones as first-line therapy - the FDA issued a warning in 2016 against their use for uncomplicated UTI due to serious and potentially disabling side effects 2. They cause significant collateral damage including alteration of fecal microbiota and C. difficile infection 2. Reserve fluoroquinolones only for pyelonephritis when local resistance is <10% and the patient hasn't used them in the past 6 months 2.
Do NOT use beta-lactams as first-line therapy - they promote rapid recurrence and damage protective periurethral and vaginal microbiota 2. Amoxicillin-clavulanate and cefpodoxime-proxetil are less effective than first-line agents 3.
Do NOT treat asymptomatic bacteriuria - treatment increases the risk of symptomatic infection, bacterial resistance, and costs 2. The only exceptions are pregnant women and patients scheduled for invasive urinary procedures 1.
Special Populations
Men with UTI
- Treat for 7-14 days (longer than women) 1, 4
- Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days is appropriate 1
- Fluoroquinolones can be prescribed according to local susceptibility testing 1
- For bacterial prostatitis, ciprofloxacin is the drug of first choice 5
Women with Diabetes
- Treat similarly to women without diabetes if no voiding abnormalities are present 3
- Use the same first-line agents for 7 days 1
Postmenopausal Women
- Use vaginal estrogen replacement to prevent recurrent UTI 1
- Same first-line antimicrobial choices apply for acute episodes 6
Treatment Duration
- Keep duration as short as reasonable, generally no longer than 7 days 1, 2
- Uncomplicated cystitis: 3-5 days depending on agent 1
- Complicated UTI: 7 days 5
- Pyelonephritis: 10-14 days 5
Resistance Considerations
The choice between first-line agents depends critically on local resistance patterns 1, 4. High resistance rates for trimethoprim-sulfamethoxazole and ciprofloxacin preclude their empiric use in many communities, particularly in patients recently exposed to these agents or at risk for ESBL-producing organisms 4. Nitrofurantoin maintains the lowest resistance rates and should be strongly considered when appropriate 2, 4.
When to Reassess
Perform urine culture and susceptibility testing if 1:
- Symptoms do not resolve by end of treatment
- Symptoms resolve but recur within 2-4 weeks
- Patient has atypical symptoms
- Suspected acute pyelonephritis
For treatment failures, assume the organism is not susceptible to the original agent and retreat with a 7-day course of a different agent 1.