What is the recommended dose and frequency of antibiotics for a typical adult patient with an uncomplicated urinary tract infection (UTI)?

Antibiotic Dosing and Duration for Uncomplicated UTI in Adults

For uncomplicated cystitis in women, use nitrofurantoin 100 mg twice daily for 5 days, fosfomycin 3 grams as a single dose, or trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days as first-line therapy. 1, 2, 3

First-Line Treatment Options for Women with Uncomplicated Cystitis

The following regimens are recommended based on their efficacy, minimal resistance patterns, and low collateral damage to intestinal flora:

Preferred First-Line Agents

• Nitrofurantoin monohydrate/macrocrystals: 100 mg orally twice daily for 5-7 days 3, 4

  • Minimal propensity for selecting resistant organisms 5
  • Effective against multidrug-resistant pathogens including ESBL-producing E. coli 1

• Fosfomycin tromethamine: 3 grams orally as a single dose 1, 3

  • Provides therapeutic urinary concentrations for 24-48 hours after single administration 1
  • Particularly useful when trimethoprim-sulfamethoxazole resistance exceeds 20-30% in the community 1
  • Resistance rates remain low at only 2.6% for initial E. coli infections 1

• Trimethoprim-sulfamethoxazole (TMP-SMX): 160/800 mg (one double-strength tablet) orally twice daily for 3 days 2, 3

  • Should only be used if local E. coli resistance rates are below 20% 6, 4
  • FDA-approved dosing for UTI is 10-14 days, but clinical trials support 3-day regimens for uncomplicated cystitis 2, 3

Alternative First-Line Agent

• Trimethoprim alone: 100 mg twice daily for 3 days 4
  • Use only when local resistance is below 20% 6

Treatment for Men with Uncomplicated UTI

Men require longer treatment duration of 7 days with the same first-line antibiotics. 7, 4

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days 4
• Nitrofurantoin 100 mg twice daily for 7 days 4
• Trimethoprim 100 mg twice daily for 7 days 4
• Always obtain urine culture before treatment to guide antibiotic selection, as men have higher rates of complicated infections 4
• Consider urethritis and prostatitis as alternative diagnoses 4

Treatment for Acute Pyelonephritis

For uncomplicated pyelonephritis in women, use ciprofloxacin 500 mg twice daily for 7 days or levofloxacin 750 mg once daily for 5 days. 7

• Fluoroquinolones remain first-line for pyelonephritis due to E. coli resistance rates still below 10% in most regions 7, 6
• Ciprofloxacin 7-day regimen showed 97% clinical cure rate versus 96% for 14-day regimen 7
• Levofloxacin 750 mg daily for 5 days demonstrated 88.3% microbiologic eradication versus 86.7% for ciprofloxacin 10 days 7
• Do not use fosfomycin for pyelonephritis - insufficient efficacy data for upper tract infections 1

Important Clinical Considerations

When to Avoid Fluoroquinolones

• Reserve fluoroquinolones for pyelonephritis and complicated infections, not uncomplicated cystitis 1, 6
• Fluoroquinolones cause significant collateral damage by selecting for multidrug-resistant pathogens 6
• Recent fluoroquinolone exposure increases resistance risk 6

Resistance Patterns That Change Management

• If patient received TMP-SMX or fluoroquinolones recently, choose alternative first-line agent due to increased resistance risk 6
• When community TMP-SMX resistance exceeds 20%, use nitrofurantoin, fosfomycin, or pivmecillinam instead 1, 6
• β-lactam agents (amoxicillin-clavulanate, cefpodoxime) are less effective as empiric first-line therapy 3

Special Populations

• Women with diabetes and uncomplicated cystitis: Treat identically to women without diabetes using standard 3-5 day regimens 3
• Adults ≥65 years: Use same first-line antibiotics and durations as younger adults, but obtain urine culture to guide therapy 4
• Pregnant women with asymptomatic bacteriuria: Use standard short-course treatment or single-dose fosfomycin 1

Catheter-Associated UTI

• 7 days of treatment for prompt symptom resolution 7
• 10-14 days for delayed response, regardless of whether catheter remains in place 7
• Levofloxacin 750 mg daily for 5 days is acceptable for non-severely ill patients with catheter-associated UTI 7
• Remove catheter as soon as clinically appropriate 7

Common Pitfalls to Avoid

• Do not use 10-14 day courses for uncomplicated cystitis in women - this is outdated and promotes resistance 3, 4
• Do not use moxifloxacin for UTI - uncertain urinary concentrations 7
• Do not treat asymptomatic bacteriuria except in pregnant women or before urologic procedures breaching mucosa 1
• Do not routinely obtain post-treatment cultures in asymptomatic patients; only if symptoms persist or recur within 2 weeks 1