What is the first-line treatment and dosage for an otherwise healthy adult patient with an uncomplicated urinary tract infection (UTI)?

First-Line Treatment for Uncomplicated UTI in Adults

For otherwise healthy adult women with uncomplicated cystitis, nitrofurantoin 100 mg twice daily for 5 days is the preferred first-line treatment, followed by fosfomycin trometamol 3 g as a single dose, or trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (only if local E. coli resistance is <20%). 1, 2

Treatment Options by Priority

First-Line Agents for Women with Uncomplicated Cystitis

Nitrofurantoin is the preferred agent due to:

• Clinical efficacy of 80% and microbiological efficacy of 78-83% 2
• Lowest risk of treatment failure compared to other first-line agents 3
• Minimal persistent resistance rates (20.2% at 3 months, 5.7% at 9 months) 1
• Dosing: 100 mg twice daily for 5 days 1

Fosfomycin trometamol as an alternative:

• Clinical efficacy of 91% and microbiological efficacy of 80% 2
• Dosing: 3 g single dose 1
• Recommended only for women with uncomplicated cystitis 1

Trimethoprim-sulfamethoxazole (TMP/SMX) should be used cautiously:

• Dosing: 160/800 mg twice daily for 3 days 1, 4
• Higher risk of treatment failure than nitrofurantoin (1.6% increased risk of prescription switch, 0.2% increased risk of pyelonephritis) 3
• Only appropriate when local E. coli resistance is <20% 1, 5
• Increasing resistance rates over time limit its utility 3

Alternative Second-Line Agents

Cephalosporins (e.g., cefadroxil):

• Dosing: 500 mg twice daily for 3 days 1
• Only if local E. coli resistance <20% 1
• Lower efficacy than first-line agents and may promote faster UTI recurrences 1, 2

Pivmecillinam (where available):

• Dosing: 400 mg three times daily for 3-5 days 1

Agents NOT Recommended as First-Line

Fluoroquinolones (ciprofloxacin, levofloxacin):

• No longer recommended as first-line therapy due to serious adverse effects and increasing resistance 1, 2
• FDA advisory warns against use for uncomplicated UTIs due to unfavorable risk-benefit ratio 1
• Should be reserved for complicated infections or when other options have failed 1, 6

Beta-lactams (amoxicillin, amoxicillin-clavulanate):

• Associated with more rapid UTI recurrences 1, 2
• Lower efficacy than other first-line agents 2

Treatment for Men with Uncomplicated UTI

Men require longer treatment duration (7 days) and should always receive antibiotics with urine culture guidance: 7

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days 1, 4
• Nitrofurantoin 100 mg twice daily for 7 days 7
• Consider urethritis and prostatitis as alternative diagnoses 7

Critical Considerations

Antimicrobial Stewardship

• Avoid treating asymptomatic bacteriuria, which increases risk of symptomatic infection and resistance 1
• Fluoroquinolones and third-generation cephalosporins cause significant "collateral damage" by selecting for multidrug-resistant pathogens 1, 5
• Reserve broad-spectrum agents for life-threatening infections 5

When to Obtain Urine Culture

Culture is NOT needed for typical uncomplicated cystitis in women with characteristic symptoms (dysuria, frequency, urgency, suprapubic pain) without vaginal discharge 7

Culture IS indicated for: 1, 7

• Symptoms not resolving by end of treatment
• Symptoms recurring within 2 weeks
• Recurrent UTIs (≥3 per year or 2 in 6 months)
• Treatment failure
• History of resistant organisms
• Men with UTI symptoms
• Atypical presentation

Treatment Failure Management

If symptoms persist or recur within 2 weeks:

• Obtain urine culture with susceptibility testing 1
• Assume organism is not susceptible to initial agent 1
• Retreat with 7-day course of different antibiotic class 1

Regional Resistance Patterns

Local antibiotic susceptibility data should guide empiric choices, as resistance patterns vary significantly by region 1, 6, 8