In a 68-year-old woman with type 2 diabetes presenting with an acute uncomplicated lower urinary tract infection and normal renal function, which antibiotic is most appropriate?

• A. Nitrofurantoin
• B. Amoxicillin
• C. Ceftriaxone
• D. Ciprofloxacin

Answer: (A)

For acute uncomplicated lower urinary tract infection in a patient with normal kidney function, the goal is an antibiotic that concentrates in urine, effectively covers the usual urinary pathogens, and minimizes unnecessary broad-spectrum use. Nitrofurantoin fits this perfectly: it achieves high urinary concentrations, primarily treats bladder infections, and has good activity against common organisms like E. coli and Staphylococcus saprophyticus. Its use for a short course (typically around five days) is appropriate when renal function is preserved, reducing systemic exposure and the risk of promoting resistance.

Amoxicillin is often unreliable for urinary pathogens due to high resistance rates, making it an uncertain choice. Ceftriaxone, while effective, is a parenteral broad-spectrum option more suited to complicated infections or when oral therapy isn’t possible, so it’s unnecessarily aggressive here. Ciprofloxacin is a fluoroquinolone with broader systemic effects and higher risk of adverse events, especially in older adults, and resistance concerns mean it’s not a first-line choice for uncomplicated cystitis when nitrofurantoin is suitable.