Is Cephalexin (Keflex) effective for treating Urinary Tract Infections (UTI)?

From the Guidelines

Keflex (cephalexin) should not be the first-line treatment for uncomplicated urinary tract infections (UTIs) due to its inferior efficacy and higher propensity for adverse effects compared to other available therapies. According to the 2010 update by the Infectious Diseases Society of America and the European Society for Microology and Infectious Diseases 1, other antibiotics such as nitrofurantoin monohydrate/macrocrystals, trimethoprim-sulfamethoxazole, and fosfomycin trometamol are preferred due to their minimal resistance and comparable efficacy.

Some key points to consider when treating UTIs include:

• The choice of antibiotic should be based on local resistance rates and the susceptibility of the infecting strain 1
• The threshold of 20% as the resistance prevalence at which an 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
• Beta-lactam agents, including cephalexin, may be appropriate in certain settings, but their use should be cautious due to inferior efficacy and more adverse effects compared to other UTI antimicrobials 1

In cases where Keflex is considered, the typical adult dosage is 500 mg taken orally every 12 hours, or 250 mg every 6 hours, for 7-14 days depending on infection severity. However, it is crucial to prioritize other recommended antibiotics over Keflex for uncomplicated UTIs, unless other options are not viable. Patients should be closely monitored for adverse effects and treatment efficacy, and a urine culture is often recommended before starting treatment to ensure the infection is susceptible to the chosen antibiotic.

From the FDA Drug Label

Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae Cephalexin is indicated for the treatment of genitourinary tract infections, including those caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae 2. Key points:

• Cephalexin is effective against certain strains of bacteria that cause UTIs
• It is essential to perform culture and susceptibility tests to ensure the bacteria are susceptible to cephalexin
• Cephalexin should only be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria 2

From the Research

Keflex for UTI

• Keflex, also known as cephalexin, is a first-generation cephalosporin antibiotic that can be used to treat urinary tract infections (UTIs) 3, 4, 5.
• According to a study published in 2020, cephalexin is a recommended second-line empiric antibiotic therapy for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females 3.
• A retrospective multicenter cohort study published in 2023 found that twice-daily cephalexin is as effective as 4-times-daily dosing for uncomplicated UTIs, with no difference in treatment failure or adverse events between the two groups 4.
• Another study published in 2020 reviewed the historical clinical trials and experimental studies of cephalexin and concluded that it has good early bacteriological and clinical cures in UTIs due to non-extended-spectrum beta-lactamase-producing Enterobacteriaceae, comparable to many traditionally first-line agents 5.
• Cephalexin can be conveniently administered as 500 mg twice or thrice daily, making it a practical choice for many clinicians 5.

Treatment Guidelines

• The Infectious Diseases Society of America recommends nitrofurantoin, trimethoprim-sulfamethoxazole, and fosfomycin as first-line antibiotic treatments for uncomplicated UTIs, and discourages the use of fluoroquinolone antibiotic agents 6, 7.
• A study published in 2021 found that guideline discordance continues in the treatment of uncomplicated UTIs, with the overuse of fluoroquinolones and the underuse of first-line antibiotic agents, including cephalexin 7.
• The same study found that obstetricians-gynecologists and urologists had a higher likelihood of concordant treatment than other specialties, and that patients aged 18-29 years and 30-44 years had a higher likelihood of receiving guideline-concordant treatment than patients aged 45-75 years 7.

Efficacy and Safety

• Cephalexin has been shown to be effective in treating UTIs caused by non-extended-spectrum beta-lactamase-producing Enterobacteriaceae, with good early bacteriological and clinical cures 5.
• The safety profile of cephalexin is generally favorable, with few reported adverse events, including diarrhea, nausea, and vomiting 4, 5.
• However, cephalexin should be used with caution in patients with a history of allergy to penicillins or other cephalosporins, and in patients with renal impairment 5.