What is the best medication for a urinary tract infection (UTI)?

Best Medication for Urinary Tract Infection (UTI)

Nitrofurantoin 100 mg twice daily for 5 days is the preferred first-line treatment for uncomplicated UTI in women, as it provides excellent efficacy while minimizing antimicrobial resistance and collateral damage to normal flora. 1, 2

First-Line Treatment Options for Uncomplicated Cystitis in Women

The following agents are recommended as first-line therapy, listed in order of preference:

• Nitrofurantoin 100 mg twice daily for 5 days is the most strongly recommended option by multiple international guidelines 1, 2
• Fosfomycin trometamol 3 grams as a single dose is an alternative first-line option, though it may have slightly lower efficacy 1, 2
• Pivmecillinam 400 mg three times daily for 3-5 days (where available) 1
• Trimethoprim-sulfamethoxazole (TMP-SMX) 160/800 mg twice daily for 3 days should ONLY be used if local E. coli resistance rates are below 20% 1

Why Nitrofurantoin is Preferred

• Nitrofurantoin maintains low resistance rates globally and causes minimal collateral damage to normal flora, making it superior for antimicrobial stewardship 2, 3
• It achieves excellent urinary concentrations despite limited systemic absorption 2
• The 5-day duration balances efficacy with minimizing adverse effects 1, 2

Second-Line Alternatives

Use these only when first-line agents cannot be used due to allergy, resistance, or contraindications:

• Cephalosporins (e.g., cefadroxil 500 mg twice daily for 3 days) if local E. coli resistance is <20% 1
• Fluoroquinolones (ciprofloxacin 250-500 mg twice daily for 3 days) should be reserved due to serious FDA warnings about tendon, muscle, joint, nerve, and CNS adverse effects 2, 4
• Beta-lactams (amoxicillin-clavulanate) have inferior efficacy and more adverse effects compared to first-line agents 1, 3

Treatment in Men

Men require longer treatment duration and different considerations:

• TMP-SMX 160/800 mg twice daily for 7 days is first-line 1
• Nitrofurantoin can be used for 7 days 5
• Always obtain urine culture before treatment, as men may have prostatitis or urethritis requiring different management 1, 5

Critical Contraindications and Caveats

• Do NOT use nitrofurantoin for pyelonephritis or upper UTIs, as it doesn't achieve adequate tissue concentrations 2
• Avoid nitrofurantoin in infants under 4 months due to hemolytic anemia risk 2
• Do NOT use nitrofurantoin in patients with creatinine clearance <30 mL/min 2
• Avoid fluoroquinolones as first-line due to FDA black box warnings and their propensity to cause antimicrobial resistance 2, 3
• Do NOT use amoxicillin or ampicillin empirically due to high resistance rates 1

When to Obtain Urine Culture

• DO obtain culture in men, recurrent UTIs, treatment failure, pregnancy, suspected pyelonephritis, or history of resistant organisms 1, 5
• DO NOT obtain culture for straightforward uncomplicated cystitis in women with typical symptoms 1, 2, 5
• DO NOT treat asymptomatic bacteriuria (except in pregnancy or before urologic procedures) 1, 2

Treatment Failure Management

If symptoms persist after completing treatment:

• Obtain urine culture and susceptibility testing 1
• Assume the organism is resistant to the initial agent 1
• Retreat with a 7-day course using a different antimicrobial class 1

Special Populations

Postmenopausal women:

• Use vaginal estrogen for prevention of recurrent UTIs 1
• Same antibiotic choices and durations as younger women 5

Elderly patients (≥65 years):

• Obtain urine culture to guide therapy 5
• Use same first-line agents and durations as younger adults 5

Recurrent UTIs (≥3 episodes/year or ≥2 in 6 months):

• Consider continuous or postcoital antimicrobial prophylaxis only after non-antimicrobial interventions fail 1
• Non-antimicrobial options include methenamine hippurate, cranberry products, D-mannose, and probiotics 1, 5