Antibiotic Treatment for Urinary Tract Infections
First-Line Therapy for Uncomplicated Cystitis in Women
For uncomplicated cystitis in women, prescribe nitrofurantoin 100 mg twice daily for 5 days, fosfomycin trometamol 3 g as a single dose, or trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days—but only use trimethoprim-sulfamethoxazole if local E. coli resistance rates are below 20%. 1, 2
Specific First-Line Regimens:
- Nitrofurantoin: 100 mg twice daily for 5 days 1
- Fosfomycin trometamol: 3 g single dose (women only) 1, 2
- Pivmecillinam: 400 mg three times daily for 3-5 days (where available) 1
Second-Line Alternatives:
- Cephalosporins (e.g., cefadroxil 500 mg twice daily for 3 days): Use only if local E. coli resistance is <20% 1
- Trimethoprim alone: 200 mg twice daily for 5 days (avoid in first trimester of pregnancy) 1
Critical Pitfall - Fluoroquinolones:
Avoid fluoroquinolones (ciprofloxacin, levofloxacin) as empiric first-line therapy for uncomplicated cystitis. 1 While highly effective, they cause significant collateral damage by selecting for multidrug-resistant organisms and should be reserved for complicated infections or documented resistant pathogens 1, 3. Resistance rates are rising even for uncomplicated UTIs 4.
Treatment for Uncomplicated Cystitis in Men
Men with uncomplicated UTI require longer treatment duration: trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days. 1, 2 Fluoroquinolones can be prescribed based on local susceptibility patterns 1.
Treatment for Uncomplicated Pyelonephritis
Oral Therapy (Mild to Moderate Cases):
For outpatient pyelonephritis, prescribe ciprofloxacin 500-750 mg twice daily for 7 days or levofloxacin 750 mg once daily for 5 days as first-line therapy. 1, 2
Alternative oral regimens:
- Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 14 days (only if susceptibility confirmed; do not use empirically) 1
- Cefpodoxime: 200 mg twice daily for 10 days (give initial IV dose of long-acting cephalosporin like ceftriaxone first) 1, 2
- Ceftibuten: 400 mg once daily for 10 days (give initial IV dose first) 1
Parenteral Therapy (Severe Cases):
For patients requiring hospitalization or IV therapy initially 1:
- Ciprofloxacin: 400 mg IV twice daily 1
- Levofloxacin: 750 mg IV once daily 1
- Ceftriaxone: 1-2 g IV once daily 1
- Cefepime: 1-2 g IV twice daily 1
- Gentamicin: 5 mg/kg IV once daily (with or without ampicillin) 1
- Piperacillin-tazobactam: 2.5-4.5 g IV three times daily 1
Reserve carbapenems and novel broad-spectrum agents (ceftolozane-tazobactam, ceftazidime-avibactam, cefiderocol) exclusively for documented multidrug-resistant organisms. 1, 3
Critical Pitfall - Avoid These for Pyelonephritis:
Never use nitrofurantoin, fosfomycin, or pivmecillinam for pyelonephritis—they do not achieve adequate tissue concentrations in the renal parenchyma. 2
Treatment Duration Principles
Treat for the shortest effective duration: generally no longer than 7 days for cystitis and 5-14 days for pyelonephritis depending on severity and agent used. 1
Specific durations:
- Uncomplicated cystitis: 3-5 days (except trimethoprim-sulfamethoxazole 14 days if used for pyelonephritis) 1
- Uncomplicated cystitis in men: 7 days 1
- Pyelonephritis with fluoroquinolones: 5-7 days 1
- Pyelonephritis with trimethoprim-sulfamethoxazole: 14 days 1
Complicated UTIs
For complicated UTIs, obtain urine culture before initiating therapy and tailor antibiotics based on susceptibility results. 1 The microbial spectrum is broader (E. coli, Proteus, Klebsiella, Pseudomonas, Enterococcus) and resistance rates are higher 1.
Empiric therapy should follow local antibiograms, with consideration of:
- Fluoroquinolones: If local resistance <10% 1
- Extended-spectrum cephalosporins or penicillins: Ceftriaxone, piperacillin-tazobactam 1
- Aminoglycosides: With or without ampicillin 1
Address the underlying urological abnormality (obstruction, foreign body, incomplete voiding) as definitive management—antibiotics alone are insufficient. 1
Special Populations
Pregnancy:
- Avoid trimethoprim in first trimester and trimethoprim-sulfamethoxazole in last trimester 1
- Nitrofurantoin and fosfomycin are safe options 1
- Always obtain urine culture in pregnant women and treat asymptomatic bacteriuria 1
Diabetes:
Women with diabetes and uncomplicated cystitis without voiding abnormalities should be treated identically to women without diabetes using standard first-line regimens. 5
Recurrent UTIs:
- Diagnose each episode with urine culture 1
- Use vaginal estrogen in postmenopausal women as prophylaxis (strong recommendation) 1
- Consider immunoactive prophylaxis, methenamine hippurate, or continuous/postcoital antibiotic prophylaxis after non-antimicrobial measures fail 1
- Do not treat asymptomatic bacteriuria except in pregnancy or before invasive urinary procedures 1
Renal Impairment:
For creatinine clearance 30-50 mL/min: Reduce ciprofloxacin to 250-500 mg every 12 hours 6 For creatinine clearance 5-29 mL/min: Ciprofloxacin 250-500 mg every 18 hours 6 For hemodialysis: Ciprofloxacin 250-500 mg every 24 hours after dialysis 6
Key Clinical Pitfalls to Avoid
Do not perform urine culture for straightforward uncomplicated cystitis in women—diagnosis is clinical based on dysuria, frequency, urgency without vaginal discharge. 2 Reserve cultures for treatment failures, recurrent infections, pyelonephritis, complicated UTIs, pregnancy, or atypical presentations 2.
Check local antibiograms before prescribing empiric therapy—resistance patterns vary significantly by region. 1, 7 Recent data shows trimethoprim resistance exceeds 20% in recurrent UTIs, making it unsuitable for empiric use in this population 7.
If symptoms persist beyond 2 weeks or recur within 2 weeks, obtain urine culture and assume the organism is resistant to the initial agent—retreat with a different antibiotic for 7 days. 1
Avoid β-lactams (amoxicillin-clavulanate, cephalexin) as first-line empiric therapy for uncomplicated cystitis—they are less effective than other options. 5