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 dosing for uncomplicated urinary tract infections is 500 mg every 12 hours for patients over 15 years of age, and therapy should be continued for 7 to 14 days 1.
- The usual adult dose is not recommended for this specific infection.
- Pediatric patients have different dosing recommendations.
From the Research
For uncomplicated urinary tract infections (UTIs), Keflex (cephalexin) is typically prescribed at a dose of 500 mg orally every 12 hours for a duration of 5-7 days, as this dosing strategy has been shown to be as effective as 4-times-daily dosing 2. This recommendation is based on a retrospective multicenter cohort study that compared the efficacy of cephalexin 500 mg twice daily (BID) with 500 mg 4 times daily (QID) for the treatment of uncomplicated UTI in adult female patients 2. The study found no difference in treatment failure between the two groups, including failure while undergoing therapy or recurrence within 30 days, and no differences in reported adverse events were observed between groups 2. It's essential to note that patients with reduced kidney function may require dose adjustments, and Keflex works by inhibiting bacterial cell wall synthesis, making it effective against many common UTI-causing organisms, particularly gram-positive bacteria and some gram-negative bacteria including Escherichia coli. Some key points to consider when prescribing Keflex for UTIs include:
- Patients should complete the entire course of antibiotics even if symptoms improve before completion to ensure complete eradication of the infection and prevent recurrence.
- It's crucial to stay well-hydrated during treatment and to take the medication with food if stomach upset occurs.
- If symptoms worsen or do not improve within 2-3 days, patients should contact their healthcare provider as this may indicate the infection is resistant to Keflex and an alternative antibiotic may be needed. Other studies have also examined the use of cephalexin for UTIs, including a review of cephalexin and cefadroxil for the treatment of acute uncomplicated lower urinary tract infection, which concluded that cephalexin has very good early bacteriological and clinical cures in uLUTIs due to non-extended-spectrum beta-lactamase-producing (ESBL) Enterobacteriaceae comparable to many traditionally first-line agents 3. However, the most recent and highest quality study, which compared twice-daily and 4-times-daily cephalexin dosing for uncomplicated UTI, supports the use of 500 mg orally every 12 hours for a duration of 5-7 days 2.