What are the recommended antibiotics for treating uncomplicated urinary tract infections (UTIs) in adults?

Antibiotic Treatment for Uncomplicated UTI in Adults

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

First-Line Treatment Options for Women with Uncomplicated Cystitis

Preferred agents (choose one):

• Nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days - This is the most strongly recommended first-line agent by multiple international guidelines 1, 2

  • Maintains 95.6% susceptibility against E. coli with only 2.3% resistance rates 3
  • Achieves combined symptomatic improvement and bacteriological cure in 77% of patients by day 3 versus 54% with placebo 4

• Fosfomycin trometamol 3 g single dose - Convenient single-dose option 1, 5

  • May have slightly inferior efficacy compared to multi-day regimens but offers excellent compliance 2
  • FDA-approved dosing: one sachet mixed with water, taken with or without food 5

• Pivmecillinam 400 mg three times daily for 3-5 days - Where available 1

Alternative First-Line Agents (When Above Cannot Be Used)

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days - ONLY if local E. coli resistance rates are below 20% 1, 2, 6

  • Rising resistance rates (averaging 29% in some communities) have relegated this from first-line status 1, 3
  • FDA-approved for 10-14 days for UTI, though 3-day regimens are guideline-recommended 6

• Trimethoprim 200 mg twice daily for 5 days - Alternative when sulfa allergy present 1

Second-Line Options (Reserve for When First-Line Agents Contraindicated)

• Cephalosporins (cefadroxil 500 mg twice daily for 3 days, or comparable agents) - Use only if local E. coli resistance <20% 1

• Fluoroquinolones should be explicitly avoided as first-line therapy despite high efficacy 1, 2

  • Ciprofloxacin and levofloxacin have 24% resistance rates and cause significant collateral damage to normal flora 3
  • FDA has issued serious safety warnings regarding tendon, muscle, joint, nerve, and CNS effects 2
  • Reserve for pyelonephritis or complicated UTIs only 2

Treatment for Men with Uncomplicated UTI

Men require longer treatment duration (7 days minimum): 1, 7

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days - First choice when local resistance permits 1, 6
• Nitrofurantoin 100 mg twice daily for 7 days - Alternative option 7
• Always obtain urine culture before treatment in men to guide antibiotic selection and rule out prostatitis 7

Critical Contraindications and Caveats

Do NOT use nitrofurantoin if:

• Creatinine clearance <60 mL/min (consider TMP-SMX or amoxicillin-clavulanate instead) 2
• Suspected pyelonephritis (fever, flank pain, systemic symptoms) - nitrofurantoin does not achieve adequate tissue concentrations 2
• Infants under 4 months of age 2

Do NOT use amoxicillin or ampicillin empirically - very high resistance rates make them inappropriate for empiric therapy 1

Do NOT use fluoroquinolones as first-line - reserve for pyelonephritis or when first-line agents fail due to resistance, allergy, or intolerance 1, 2

When to Obtain Urine Culture

Culture is NOT needed for:

• Typical uncomplicated cystitis in women with classic symptoms (dysuria, frequency, urgency, suprapubic pain) and no vaginal discharge 2, 7

Culture IS required for:

• All men with UTI symptoms 7
• Women with recurrent UTI (≥3 UTIs/year or 2 in 6 months) 1
• Treatment failure or symptom recurrence within 2 weeks 1, 2
• Atypical presentation or suspected resistant organisms 7
• History of resistant isolates 7

Treatment Failure Management

If symptoms persist after completing treatment:

• Obtain urine culture with susceptibility testing 1
• Assume the organism is not susceptible to the original agent 1
• Retreat with a 7-day regimen using a different antibiotic class 1

Special Considerations for Recurrent UTI

For women with recurrent UTI (≥3 episodes/year):

• Vaginal estrogen replacement in postmenopausal women (strong recommendation) 1
• Methenamine hippurate for prevention 1, 7
• Immunoactive prophylaxis 1
• Continuous or postcoital antimicrobial prophylaxis only after non-antimicrobial interventions fail 1
• Patient-initiated self-start therapy with pre-prescribed antibiotics is appropriate for select patients 2