What alternative antibiotic should be prescribed for a 65-year-old female with a persistent urinary tract infection (UTI) that did not respond to Cephalexin (Keflex)?

From the Guidelines

For a 65-year-old female with a recurrent urinary tract infection that failed to respond to Keflex (cephalexin), I would recommend switching to nitrofurantoin (Macrobid) 100 mg twice daily for 5 days, as it is an appropriate choice for therapy due to minimal resistance and propensity for collateral damage, with efficacy comparable to trimethoprim-sulfamethoxazole 1. When considering alternative treatments, it's essential to weigh the benefits and risks of each option.

• Trimethoprim-sulfamethoxazole (160/800 mg [1 double-strength tablet] twice-daily for 3 days) is another appropriate choice for therapy, given its efficacy as assessed in numerous clinical trials, if local resistance rates of uropathogens causing acute uncomplicated cystitis do not exceed 20% or if the infecting strain is known to be susceptible 1.
• Fluoroquinolones, such as ciprofloxacin, are highly efficacious but have a propensity for collateral damage and should be reserved for important uses other than acute cystitis 1.
• The choice of antibiotic should be guided by local resistance patterns, the patient's medication allergies, kidney function, and medication interactions.
• A urine culture should be obtained before starting the new antibiotic to identify the specific pathogen and its antibiotic sensitivities.
• The patient should complete the entire course of antibiotics even if symptoms improve, drink plenty of fluids, and follow up if symptoms persist after treatment completion. It's crucial to note that the threshold of 20% as the resistance prevalence at which the agent is no longer recommended for empirical treatment of acute cystitis is based on expert opinion derived from clinical, in vitro, and mathematical modeling studies 1. In this case, considering the patient's recent treatment with Keflex and the potential for resistance, nitrofurantoin (Macrobid) 100 mg twice daily for 5 days is a reasonable alternative, as it has minimal resistance and propensity for collateral damage, with efficacy comparable to trimethoprim-sulfamethoxazole 1.

From the FDA Drug Label

The overall eradication rates for pathogens of interest are presented in Table 19. The bacteriologic cure rates overall for levofloxacin and control at the test-of-cure (TOC) visit for the group of all patients with a documented pathogen at baseline (modified intent to treat or mITT) and the group of patients in the mITT population who closely followed the protocol (Microbiologically Evaluable) are summarized in Table 20. Microbiologic eradication rates in the Microbiologically Evaluable population at TOC for individual pathogens recovered from patients randomized to levofloxacin treatment are presented in Table 21.

The patient has already been given Keflex, which was not effective. Levofloxacin could be considered as an alternative antibiotic for the treatment of the urinary tract infection, given its efficacy in treating various bacterial infections, including those caused by Gram-negative and Gram-positive bacteria. However, the choice of antibiotic should be based on the specific pathogen and its susceptibility pattern.

• Key considerations:
  • The patient's age and potential underlying health conditions should be taken into account when selecting an antibiotic.
  • The potential for resistance to levofloxacin should be considered, especially if the patient has previously been treated with fluoroquinolones.
  • The patient should be monitored for potential side effects, such as tendonitis or tendon rupture, which are more common in older adults.
  • It is essential to obtain a culture and susceptibility test to guide the selection of the most appropriate antibiotic 2.

From the Research

Treatment Options for Urinary Tract Infection

The patient has already been treated with Keflex (cephalexin) for a urinary tract infection, but it did not resolve the issue. Considering the provided studies, the following options can be explored:

• Cephalexin can be administered at a different dosage, as studies have shown that twice-daily dosing is as effective as four-times-daily dosing for uncomplicated urinary tract infections (uUTIs) 3, 4.
• Alternative antibiotics can be considered, such as ceftriaxone, which has been shown to be effective in treating E. coli urinary tract infections 5.
• The choice of antibiotic should be based on local antibiogram data and the specific characteristics of the patient's infection.

Antibiotic Resistance and Treatment Failure

It is essential to consider antibiotic resistance when selecting a treatment option. Studies have highlighted the increasing resistance rates to fluoroquinolones, such as levofloxacin, among uropathogenic Escherichia coli strains 5.

• Treatment failure rates have been compared between different antibiotics, including cephalexin and levofloxacin, with no significant difference in hospital length of stay or hospital cost 5.
• The effectiveness of cephalexin in treating uUTIs has been demonstrated, with high bacteriological and clinical cure rates, especially against non-extended-spectrum beta-lactamase-producing (ESBL) Enterobacteriaceae 6.

Dosing and Administration

The dosing and administration of cephalexin can impact treatment outcomes and patient adherence:

• Twice-daily dosing of cephalexin has been shown to be as effective as four-times-daily dosing for uUTIs, which may improve patient adherence 3, 4.
• Cephalexin can be conveniently administered as 500 mg twice or thrice daily, making it a practical choice for many clinicians 6.