What is the recommended dose of Cephalexin (Keflex) for a urinary tract infection (UTI)?

From the Guidelines

For a urinary tract infection (UTI), the recommended dose of Cephalexin (Keflex) is 500 mg taken orally every 12 hours, or 250 mg every 6 hours, for 7-14 days depending on infection severity. This recommendation is based on the guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women, which suggest that beta-lactam agents, including cephalexin, may be appropriate choices for therapy when other recommended agents cannot be used 1. However, it is essential to note that beta-lactams generally have inferior efficacy and more adverse effects compared to other UTI antimicrobials 1.

Important Considerations

• The dosage for children is based on weight, typically 25-50 mg/kg/day divided into 2-4 doses.
• It is crucial to take the full course of antibiotics even if symptoms improve to prevent recurrence or antibiotic resistance.
• Patients should drink plenty of water during treatment to help flush bacteria from the urinary tract.
• Those with kidney disease may require dose adjustments, and patients with penicillin allergies should use caution as cross-reactivity can occur.

Key Points to Keep in Mind

• Cephalexin works by inhibiting bacterial cell wall synthesis, making it effective against many common UTI-causing bacteria, particularly gram-positive organisms and some gram-negative bacteria like E. coli.
• If patients experience severe side effects like rash, difficulty breathing, or severe diarrhea, they should seek medical attention immediately.
• The treatment duration may vary depending on the severity of the infection, with uncomplicated UTIs typically requiring a 7-day course and complicated infections requiring the full 14 days.

From the FDA Drug Label

For the following infections, a dosage of 500 mg may be administered every 12 hours: ... and uncomplicated cystitis in patients over 15 years of age. Cystitis therapy should be continued for 7 to 14 days. The recommended dose of Cephalexin (Keflex) for a urinary tract infection (UTI), specifically uncomplicated cystitis, is 500 mg every 12 hours for patients over 15 years of age, and therapy should be continued for 7 to 14 days 2.

From the Research

Cephalexin Dosage for Urinary Tract Infections

• The recommended dose of Cephalexin for a urinary tract infection (UTI) is not explicitly stated in the provided studies 3, 4.
• However, a study published in 2023 5 compared the effectiveness of Cephalexin 500mg twice daily (BID) and 500mg four times daily (QID) for the treatment of uncomplicated UTIs in females.
• The results showed that twice-daily Cephalexin is as effective as 4-times-daily dosing for uncomplicated UTIs, with no significant difference in treatment failure or adverse events between the two groups 5.
• Another study published in 1987 6 mentioned that Cephalexin is one of the cephalosporins that can be used to treat urinary tract infections, but did not provide specific dosage recommendations.
• The optimal characteristics of agents to treat uncomplicated urinary tract infections, including high urinary levels and minimal side effects, were discussed in a study published in 1992 7.

Treatment of Urinary Tract Infections

• The treatment of urinary tract infections depends on the severity and type of infection, as well as the patient's medical history and other factors 3, 4.
• For uncomplicated acute cystitis in women, guidelines recommend nitrofurantoin, trimethoprim-sulfamethoxazole, fosfomycin, or pivmecillinam as first-line therapies 3, 4.
• Third-generation cephalosporins are preferred for the management of pyelonephritis 3.
• The choice of antibiotic and dosage regimen should be based on the severity of the infection, the patient's medical history, and the susceptibility of the causative organism 6.