What antibiotic is recommended for treating an uncomplicated urinary tract infection (UTI)?

Treatment of Uncomplicated Urinary Tract Infections

Nitrofurantoin 100 mg twice daily for 5 days is the recommended first-line treatment for uncomplicated urinary tract infections due to its effectiveness and low resistance rates. 1

First-Line Treatment Options

Uncomplicated UTIs should be treated with a short course of one of these first-line antibiotics:

1. Nitrofurantoin

   • Dosage: 100 mg twice daily
   • Duration: 5 days
   • Advantages: High effectiveness, low resistance rates
   • Contraindications: Renal impairment, last trimester of pregnancy, CrCl <30 mL/min
   • Evidence quality: High 1, 2

2. Trimethoprim-sulfamethoxazole (TMP-SMX)

   • Dosage: 160/800 mg (one DS tablet) twice daily
   • Duration: 3 days
   • Only use if local resistance rates <20%
   • FDA-approved for UTIs caused by E. coli, Klebsiella, Enterobacter, Morganella morganii, Proteus mirabilis, and Proteus vulgaris 3

3. Fosfomycin

   • Dosage: 3 g single dose
   • Advantages: Convenient single-dose treatment
   • Evidence quality: Moderate 1, 4

Second-Line Treatment Options

When first-line agents cannot be used due to allergies, resistance, or other contraindications:

• Pivmecillinam: 400 mg twice daily for 5 days 1, 4
• Amoxicillin-clavulanate: 500/125 mg twice daily for 3-7 days 1
• Cephalexin: 500 mg four times daily for 5-7 days 1
• Fluoroquinolones (e.g., ciprofloxacin 500-750 mg twice daily for 7 days or levofloxacin 750 mg once daily for 5 days)
  • Note: Should not be used as first-line therapy due to increasing resistance and risk of adverse effects 1, 5

Special Considerations

Renal Impairment

• Avoid nitrofurantoin if CrCl <30 mL/min
• For TMP-SMX, adjust dosing based on creatinine clearance:
  • CrCl >30 mL/min: Standard regimen
  • CrCl 15-30 mL/min: Half the usual regimen
  • CrCl <15 mL/min: Not recommended 3

Pregnancy

• Nitrofurantoin is generally safe except in the last trimester
• Avoid TMP-SMX in first and third trimesters
• Consider cephalexin as an alternative 1

Elderly Patients

• May present with atypical symptoms (confusion, falls, functional decline)
• Consider renal function when selecting antibiotics
• Monitor for adverse effects, particularly with nitrofurantoin 1, 2

Treatment Algorithm

1. Obtain urine culture before starting antibiotics when possible
2. Start empiric therapy with nitrofurantoin 100 mg twice daily for 5 days
3. If nitrofurantoin contraindicated:
   • Use TMP-SMX if local resistance <20%
   • Use fosfomycin as single-dose alternative
4. Adjust therapy based on culture results and clinical response
5. For treatment failure, switch to an alternative agent based on susceptibility testing

Common Pitfalls to Avoid

1. Treating asymptomatic bacteriuria: Do not treat unless patient is pregnant or undergoing urologic procedures 1
2. Overuse of fluoroquinolones: Reserve for cases where first-line agents cannot be used due to increasing resistance 1, 5
3. Inadequate treatment duration: Follow recommended durations to ensure complete eradication while minimizing resistance
4. Ignoring local resistance patterns: Consider community antibiotic resistance when selecting empiric therapy 5
5. Failure to adjust for renal function: Particularly important with nitrofurantoin and TMP-SMX 3

By following these evidence-based recommendations, uncomplicated UTIs can be effectively treated while minimizing antibiotic resistance and adverse effects.