What antibiotics are recommended for treating urinary tract infections (UTIs)?

Recommended Antibiotics for Urinary Tract Infections

First-Line Treatment for Uncomplicated Cystitis in Women

For uncomplicated cystitis in women, nitrofurantoin (100 mg twice daily for 5 days), fosfomycin trometamol (3g single dose), or trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) are the recommended first-line agents, with selection based on local resistance patterns. 1, 2

Specific First-Line Regimens

• Fosfomycin trometamol: 3g single dose, particularly effective and convenient for uncomplicated cystitis 1, 2
• Nitrofurantoin: Multiple formulations available 1, 2:
  • Macrocrystals: 50-100 mg four times daily for 5 days
  • Monohydrate or macrocrystals: 100 mg twice daily for 5 days
  • Prolonged release: 100 mg twice daily for 5 days
• Pivmecillinam: 400 mg three times daily for 3-5 days (where available) 1, 2
• Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 3 days (only if local E. coli resistance is <20%) 1, 2

Important Caveat on TMP-SMX

High rates of resistance to trimethoprim-sulfamethoxazole in many communities preclude its use as empiric therapy, particularly in patients recently exposed to antibiotics or at risk for ESBL-producing organisms 3. Always verify local resistance patterns before prescribing 2.

Second-Line Treatment Options

When first-line agents cannot be used due to allergy, intolerance, or resistance patterns, consider these alternatives 1, 2:

• Cephalosporins (e.g., cefadroxil 500 mg twice daily for 3 days): Only when local E. coli resistance is <20% 1, 2
• Trimethoprim alone: 200 mg twice daily for 5 days (contraindicated in first trimester of pregnancy) 1
• Amoxicillin-clavulanic acid: Alternative when first-line agents are unsuitable 1, 2

Treatment for Men with UTIs

Men with UTIs require longer treatment duration (7 days) compared to women, with trimethoprim-sulfamethoxazole (160/800 mg twice daily) as the preferred first-line agent. 1, 2

• Fluoroquinolones may be considered based on local susceptibility patterns, but should be restricted due to FDA warnings about serious adverse effects 1, 2

Upper Urinary Tract Infections (Pyelonephritis)

Mild to Moderate Pyelonephritis

Ciprofloxacin is recommended as first-choice for mild-to-moderate pyelonephritis, but only if local resistance patterns permit its use. 1

• First choice: Ciprofloxacin (if local resistance allows) 1
• Second choice: Ceftriaxone or cefotaxime 1

Severe Pyelonephritis

For severe cases requiring parenteral therapy 1:

• First choice: Ceftriaxone or cefotaxime 1
• Second choice: Amikacin (preferred over gentamicin due to better resistance profile against ESBL-producing organisms) 1

Critical FDA Warning on Fluoroquinolones

The FDA has issued serious safety warnings about fluoroquinolones, including risks of tendon rupture, muscle damage, joint problems, nerve damage, and central nervous system effects 1, 2. Fluoroquinolones should be reserved for situations where benefits clearly outweigh risks and no safer alternatives exist. 1, 2

Recurrent UTIs (rUTIs)

Diagnostic Approach

Always obtain urine culture and antimicrobial susceptibility testing for recurrent UTIs before initiating treatment. 1, 2

• Assume the infecting organism is not susceptible to the originally used agent 1
• Retreatment should use a 7-day regimen with a different agent 1

Treatment Strategy

First-line agents remain the same (nitrofurantoin, TMP-SMX, fosfomycin) but must be guided by culture results 2. For organisms resistant to oral antibiotics, culture-directed parenteral therapy may be necessary 2.

Prevention Strategies

Before resorting to long-term antibiotic prophylaxis, consider non-antibiotic preventive measures 1, 2:

• Vaginal estrogen replacement in postmenopausal women (strong recommendation) 1
• Immunoactive prophylaxis to reduce recurrence in all age groups (strong recommendation) 1
• Methenamine hippurate for women without urinary tract abnormalities (strong recommendation) 1
• Increased fluid intake in premenopausal women 1
• Probiotics containing strains with proven efficacy 1
• Cranberry products (weak evidence, contradictory findings) 1

Antibiotic Prophylaxis

Only use continuous or postcoital antimicrobial prophylaxis when non-antimicrobial interventions have failed. 1, 2

• Effective agents for prophylaxis include nitrofurantoin 50mg, trimethoprim 100mg, or norfloxacin 200mg at night 4
• Self-administered short-term therapy should be considered for patients with good compliance 1

Critical Clinical Pearls

Local Resistance Patterns

Always consult local antibiograms before selecting empiric therapy, as regional resistance variations significantly impact treatment success. 2 This is the single most important factor in antibiotic selection.

Avoid Treating Asymptomatic Bacteriuria

Do not treat asymptomatic bacteriuria except in pregnant women and patients undergoing invasive urologic procedures 2. This practice contributes unnecessarily to antimicrobial resistance.

When to Obtain Cultures

Obtain urine cultures before treatment in 2:

• Recurrent UTIs
• Treatment failures
• Atypical presentations
• Symptoms not resolving by end of treatment
• Symptoms recurring within 2 weeks 1

Treatment Duration Matters

Short-course therapy (3-5 days) is sufficient for uncomplicated cystitis in women 2. Single-dose antibiotics (except fosfomycin) show higher rates of bacteriological persistence compared to short-course therapy 2.

Antimicrobial Stewardship

Balance symptom resolution with minimizing resistance development 2. The growing problem of antimicrobial resistance demands judicious antibiotic use, particularly avoiding fluoroquinolones and broad-spectrum agents when narrower-spectrum options are effective 3, 5.