What antibiotic is recommended for a 64-year-old female patient with a urinary tract infection (UTI) and a 4 mm renal calculus (kidney stone)?

From the Guidelines

For a 64-year-old female with a UTI and a 4 mm kidney stone, I recommend empiric treatment with nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5 days) as the first-line therapy due to its minimal resistance and efficacy comparable to trimethoprim-sulfamethoxazole 1. The choice of antibiotic should be guided by local resistance patterns and urine culture results.

• Nitrofurantoin is a suitable option for uncomplicated cystitis, with a low propensity for collateral damage and minimal resistance 1.
• Trimethoprim-sulfamethoxazole (160/800 mg twice-daily for 3 days) is an alternative option, but its use should be based on local resistance rates of uropathogens, which should not exceed 20% 1.
• Fluoroquinolones, such as ciprofloxacin, are highly efficacious but have a propensity for collateral damage and should be reserved for alternative uses 1.
• The patient's kidney function should be considered when choosing an antibiotic, and nitrofurantoin is generally a safe option for patients with normal kidney function.
• Additionally, the patient should be advised to strain her urine, maintain hydration with 2-3 liters of fluid daily, and use pain management as needed (ibuprofen 400-600 mg every 6-8 hours or prescription pain medication) to help pass the kidney stone.
• Follow-up imaging is recommended in 2-4 weeks to confirm stone passage, and urological intervention may be necessary if the stone doesn't pass within 4-6 weeks or if symptoms worsen.

From the FDA Drug Label

To reduce the development of drug-resistant bacteria and maintain the effectiveness of sulfamethoxazole and trimethoprim tablets and other antibacterial drugs, sulfamethoxazole and trimethoprim tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to empiric selection of therapy Urinary Tract Infections For the treatment of urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis and Proteus vulgaris

Trimethoprim-sulfamethoxazole (PO) can be considered for the treatment of the patient's urinary tract infection, as it is indicated for the treatment of urinary tract infections due to susceptible strains of certain organisms, including Escherichia coli and Klebsiella species. However, the choice of antibiotic should be guided by culture and susceptibility information when available, and local epidemiology and susceptibility patterns in their absence 2.

• The presence of a 4 mm kidney stone is not directly relevant to the choice of antibiotic for the UTI.
• The patient's age (64 years old) is not a contraindication for the use of trimethoprim-sulfamethoxazole.

From the Research

Treatment Options for UTI

• The recommended first-line empiric antibiotic therapy for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females is a 5-day course of nitrofurantoin, a 3-g single dose of fosfomycin tromethamine, or a 5-day course of pivmecillinam 3.
• However, the patient has a history of kidney stones, which may increase the likelihood of resistance to nitrofurantoin 4.
• Considering the patient's age (64 years) and kidney stone history, alternative antibiotic therapies may be necessary.

Considerations for Nitrofurantoin Use

• Nitrofurantoin is commonly used to treat uncomplicated urinary tract infections, but its use in patients with reduced kidney function may result in subtherapeutic urine concentrations 5.
• However, a study found that mild or moderate reductions in estimated glomerular filtration rate did not justify avoidance of nitrofurantoin 5.
• The American Geriatrics Society recommends nitrofurantoin for short-term use in patients with a creatinine clearance greater than or equal to 30 mL/min 6.

Alternative Treatment Options

• Other first-line treatment options for UTI include fosfomycin and trimethoprim-sulfamethoxazole (when resistance levels are <20%) 7.
• Second-line options include oral cephalosporins, fluoroquinolones, and β-lactams, such as amoxicillin-clavulanate 3.
• The choice of antibiotic should be based on the patient's specific needs, medical history, and local susceptibility patterns.