Duration of Keflex (Cephalexin) Treatment
For most infections, Keflex (cephalexin) should be taken for 7-10 days, with specific durations determined by the type of infection being treated. 1, 2
Standard Treatment Durations by Infection Type
- Streptococcal pharyngitis: 10 days of therapy is required to achieve maximal pharyngeal eradication of Group A Streptococcus 2
- Skin and soft tissue infections: 7-10 days, depending on clinical response 2
- Uncomplicated cystitis in patients over 15 years: 7-14 days 1
- Otitis media: 10 days (dosage of 75-100 mg/kg/day in 4 divided doses is required) 1
- Beta-hemolytic streptococcal infections: At least 10 days to prevent complications such as rheumatic fever 1, 2
Dosing Considerations
Adults
- Standard dosage: 250 mg every 6 hours (1 g daily) 1
- For more severe infections: 500 mg every 12 hours or 500 mg every 6 hours (1-2 g daily) 1
- Maximum daily dose: 4 g 1
Children
- Standard dosage: 25-50 mg/kg/day in divided doses 1
- For streptococcal pharyngitis and skin infections: Total daily dose may be divided and administered every 12 hours 1
- For otitis media: 75-100 mg/kg/day in 4 divided doses 1
Important Clinical Considerations
- Complete the full course: Even if symptoms improve before the prescribed duration is completed, the full course should be taken to prevent relapse and antimicrobial resistance 2
- First-line vs. alternative use: Cephalexin is considered a narrow-spectrum cephalosporin and is preferred over broad-spectrum cephalosporins when treating penicillin-allergic patients (except those with immediate hypersensitivity reactions) 2
- Efficacy with different dosing schedules: Studies have shown that twice-daily dosing of cephalexin can be as effective as four-times-daily dosing for certain infections, which may improve medication adherence 3, 4
Special Populations
- Renal impairment: Dosage adjustments may be necessary in patients with severe renal dysfunction 5
- Penicillin allergy: Cephalexin is often used as an alternative in penicillin-allergic patients, but should be avoided in those with immediate (anaphylactic-type) hypersensitivity to penicillin (up to 10% cross-reactivity) 2
Common Pitfalls to Avoid
- Inadequate duration: Shorter courses may lead to treatment failure, especially for streptococcal infections where a full 10-day course is necessary to prevent complications 2
- Premature discontinuation: Stopping therapy when symptoms resolve but before completing the prescribed course may lead to recurrence of infection 2
- Inappropriate dosing intervals: While twice-daily dosing may be appropriate for some infections, others require more frequent administration for optimal efficacy 1, 4
Remember that the suspension form of cephalexin should be refrigerated after mixing and may be kept for 14 days without significant loss of potency 1.