What is the best antibiotic for an adult patient with an uncomplicated urinary tract infection (UTI)?

Best Antibiotic for Uncomplicated UTI in Adults

For women with uncomplicated cystitis, prescribe nitrofurantoin 100 mg twice daily for 5 days as the first-line treatment. 1

First-Line Treatment Options for Women with Uncomplicated Cystitis

The most strongly recommended first-line agents are:

• Nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days is the preferred first-line agent due to excellent efficacy and minimal antimicrobial resistance 2, 1
• Fosfomycin trometamol 3 g as a single dose offers convenient single-dose therapy, though it may have slightly inferior efficacy compared to multi-day regimens 1, 3
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days can be used ONLY if local E. coli resistance rates are below 20% 2, 1, 4

Critical Contraindications for Nitrofurantoin

Do not use nitrofurantoin in patients with:

• Creatinine clearance less than 60 mL/min 1
• Suspected pyelonephritis 1
• Infants under 4 months of age 1

Avoid These Common Pitfalls

• Fluoroquinolones should NOT be used as first-line therapy for uncomplicated cystitis due to high resistance rates, significant adverse effects, and collateral damage to normal flora 2, 1
• Amoxicillin or ampicillin should NOT be used empirically due to high resistance rates 1
• Fluoroquinolones should be reserved exclusively for pyelonephritis or complicated UTIs 1

Treatment for Men with Uncomplicated UTI

Men require different management:

• Always obtain urine culture and susceptibility testing before or at the time of treatment initiation 1, 3
• Minimum treatment duration is 7 days (longer than women) 1, 3
• First-line options include trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days OR nitrofurantoin 100 mg twice daily for 7 days 1, 3
• Consider urethritis and prostatitis in the differential diagnosis for men with UTI symptoms 3

Treatment for Uncomplicated Pyelonephritis

For outpatient management of pyelonephritis in women and men:

• Fluoroquinolones for 5-7 days: Ciprofloxacin 500-750 mg twice daily for 7 days OR levofloxacin 750 mg once daily for 5 days 2
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days based on antibiotic susceptibility 2
• Recent evidence supports that 5-day fluoroquinolone courses are noninferior to 10-day courses, with clinical cure rates exceeding 93% 2

When Hospitalization is Required

For patients requiring intravenous therapy, initial regimens include:

• Fluoroquinolones (ciprofloxacin 400 mg twice daily or levofloxacin 750 mg daily) 2
• Aminoglycosides with or without ampicillin 2
• Extended-spectrum cephalosporins (ceftriaxone 1-2 g daily or cefepime 1-2 g twice daily) 2
• Carbapenems should be reserved ONLY for patients with early culture results indicating multidrug-resistant organisms 2

When to Obtain Urine Culture

Urine culture is required for:

• All men with UTI symptoms 1, 3
• Women with recurrent UTI 1
• Treatment failure 1
• Symptom recurrence within 2 weeks 1
• Atypical presentation 3
• History of resistant isolates 3

Management of Treatment Failure

If symptoms persist after completing treatment:

• Obtain urine culture with susceptibility testing 1
• Retreat with a 7-day regimen using a different antibiotic class 1

Prevention of Recurrent UTI

For postmenopausal women with recurrent infections:

• Vaginal estrogen replacement is strongly recommended 1
• Methenamine hippurate can be considered 1, 3
• Increased fluid intake and cranberry products may help prevent recurrence 3
• Continuous or postcoital antimicrobial prophylaxis is effective but carries risks of adverse effects and antimicrobial resistance 3

Special Considerations for Older Adults

For nonfrail adults 65 years and older with no relevant comorbidities:

• Urine culture with susceptibility testing is necessary to adjust antibiotic choice after initial empiric treatment 3
• First-line antibiotics and treatment durations do not differ from those recommended for younger adults 3