What is the drug of choice for a community‑acquired uncomplicated urinary tract infection in an elderly adult with estimated glomerular filtration rate ≥ 60 mL/min and no known drug allergies?

First-Line Treatment for Uncomplicated UTI in Elderly Adults

Nitrofurantoin 100 mg orally twice daily for 5–7 days is the preferred first-line antibiotic for treating community-acquired uncomplicated urinary tract infections in elderly adults with normal renal function (eGFR ≥60 mL/min). 1, 2

Why Nitrofurantoin is Preferred in This Population

• Resistance rates remain exceptionally low (<5%) even after decades of use, making it more reliable than alternatives like trimethoprim-sulfamethoxazole (29% resistance) or fluoroquinolones (24% resistance). 2, 3

• Nitrofurantoin achieves high urinary concentrations and causes minimal disruption to gut flora, reducing the risk of Clostridioides difficile infection and preserving the microbiome—particularly important in elderly patients on multiple medications. 1, 2

• The drug maintains 95.6% susceptibility against E. coli, the most common uropathogen in elderly women, with only a 2.3% resistance rate over multi-year surveillance. 3

Alternative First-Line Options

• Fosfomycin trometamol 3 g as a single oral dose is an excellent alternative, especially when adherence is a concern or when any degree of renal impairment exists, because it maintains therapeutic urinary concentrations regardless of kidney function and requires no dose adjustment. 1, 4

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days may be used only if local E. coli resistance is <20% and the patient has had no recent exposure to this agent in the past 3 months. 1, 5

Critical Renal Function Considerations

• Nitrofurantoin is contraindicated when creatinine clearance falls below 30 mL/min because urinary drug concentrations become subtherapeutic and pulmonary toxicity risk increases. 6, 7

• Between 30–60 mL/min creatinine clearance, nitrofurantoin can be used for short-term therapy (5–7 days) based on updated American Geriatrics Society Beers criteria, though fosfomycin becomes the safer choice in this range. 7

• Calculate creatinine clearance using the Cockcroft-Gault equation before prescribing, as serum creatinine alone may appear normal in elderly patients despite significant underlying renal impairment due to reduced muscle mass. 8

Agents to Avoid as First-Line Therapy

• Fluoroquinolones (ciprofloxacin, levofloxacin) should be reserved for second-line use because of rising resistance (24%), serious adverse effects in the elderly (tendon rupture, peripheral neuropathy, QT prolongation, CNS effects), and substantial microbiome disruption. 1, 3

• Amoxicillin or ampicillin alone should never be used empirically due to worldwide resistance rates exceeding 50%. 1

• β-lactam agents (including amoxicillin-clavulanate and first-generation cephalosporins) have inferior efficacy with clinical failure rates of 15–30% compared to nitrofurantoin or fosfomycin. 1

Treatment Duration and Monitoring

• Nitrofurantoin requires a minimum of 5–7 days; shorter courses (3 days) are associated with higher failure rates and should be avoided. 1, 2

• Reassess clinical response within 48–72 hours; if symptoms persist or worsen, obtain a urine culture with susceptibility testing and consider imaging to rule out obstruction, stones, or abscess. 1

• No routine follow-up culture is needed for uncomplicated cystitis that resolves clinically, but elderly patients with recurrent UTIs (≥2 episodes in 6 months or ≥3 in 12 months) should have each episode documented with culture to monitor resistance patterns. 1

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria, which occurs in 15–50% of elderly patients and provides no clinical benefit when treated—it only promotes resistance and exposes patients to drug toxicity. 1

• Do not prescribe antibiotics based on pyuria alone without accompanying urinary symptoms (dysuria, frequency, urgency, fever >38.3°C, or gross hematuria); the presence of pyuria has very low positive predictive value in the elderly. 1

• Do not assume all positive urine cultures represent infection; distinguish true UTI from asymptomatic bacteriuria by requiring both symptoms and pyuria before initiating therapy. 1

• Avoid nitrofurantoin for long-term prophylaxis in elderly patients due to cumulative pulmonary and hepatic toxicity risks (0.001% serious pulmonary toxicity, 0.0003% hepatic toxicity). 1