What are the first-line antibiotics for treating acute uncomplicated cystitis?

First-Line Antibiotics for Acute Uncomplicated Cystitis

Nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5 days) is the recommended first-line antibiotic for acute uncomplicated cystitis due to minimal resistance and limited collateral damage. 1

First-Line Treatment Options

• Nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5 days) is the primary first-line agent with clinical cure rates of 88-93% and bacterial cure rates of 81-92% 1, 2
• Trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) is an appropriate first-line therapy only when local resistance rates of uropathogens are known to be <20% or the infecting strain is confirmed susceptible 1, 3
• Fosfomycin trometamol (3 g single dose) is an appropriate alternative first-line option with minimal resistance, though it may have slightly inferior efficacy compared to standard short-course regimens 1, 2
• Pivmecillinam (400 mg twice daily for 3-7 days) is recommended in regions where available (primarily European countries, not available in North America) 1

Comparative Efficacy

• Nitrofurantoin has shown similar clinical cure rates to ciprofloxacin (93% vs 95%) and trimethoprim-sulfamethoxazole (93% vs 95%) 1
• Fosfomycin demonstrates clinical cure rates of approximately 90%, but microbiological cure rates may be lower (78%) compared to nitrofurantoin (86%) 2
• FDA data shows fosfomycin is equivalent to nitrofurantoin but inferior to ciprofloxacin and trimethoprim-sulfamethoxazole in microbiological eradication rates 4
• Trimethoprim-sulfamethoxazole shows significantly reduced efficacy against resistant organisms (clinical cure rates of 41-54% for resistant strains vs 84-88% for susceptible strains) 1, 3

Alternative Treatment Options

• Fluoroquinolones (ofloxacin, ciprofloxacin, norfloxacin, levofloxacin) are highly effective in 3-day regimens but should be reserved as alternative agents due to their propensity for collateral damage and to preserve their efficacy for more serious infections 1, 2
• β-Lactam agents (amoxicillin-clavulanate, cefdinir, cefaclor, cefpodoxime-proxetil) in 3-7 day regimens should be used only when first-line agents cannot be used, as they generally have inferior efficacy and more adverse effects 1, 5

Treatments to Avoid

• Amoxicillin or ampicillin should not be used for empirical treatment due to poor efficacy and high prevalence of antimicrobial resistance worldwide 1
• Using fluoroquinolones as first-line therapy despite their high efficacy should be avoided, as this promotes resistance to these important agents needed for more serious infections 2, 6

Special Considerations

• The threshold of 20% resistance prevalence for trimethoprim-sulfamethoxazole is based on expert opinion from clinical, in vitro, and mathematical modeling studies 1
• When choosing an empiric agent, consider local resistance patterns, patient allergies, potential side effects, and cost 1
• For patients with both penicillin and sulfa allergies, nitrofurantoin and fosfomycin are the preferred options 2
• Fosfomycin is specifically indicated only for uncomplicated urinary tract infections (acute cystitis) in women due to susceptible strains of Escherichia coli and Enterococcus faecalis, not for pyelonephritis 4

Treatment Duration

• Nitrofurantoin requires 5 days of treatment 1, 7
• Trimethoprim-sulfamethoxazole is effective with 3 days of treatment 1
• Fosfomycin is administered as a single 3 g dose 4
• Fluoroquinolones are effective in 3-day regimens 1, 8
• β-Lactams require 3-7 days of treatment 1

Common Pitfalls to Avoid

• Using trimethoprim-sulfamethoxazole empirically in areas with high resistance rates (>20%) can lead to treatment failure 3
• Not obtaining cultures before treatment in chronic or recurrent cases may lead to inappropriate antibiotic selection 3
• Prescribing longer treatment durations than recommended by guidelines (a common practice observed in primary care settings) 6
• Using antibiotics with broad-spectrum activity when narrow-spectrum options would be effective, contributing to antimicrobial resistance 6, 9