Keflex (Cephalexin) for Skin Infections
Yes, Keflex (cephalexin) provides excellent coverage for most common skin infections, particularly those caused by Staphylococcus aureus and Streptococcus pyogenes, which are the predominant pathogens in non-purulent skin and soft tissue infections. 1
FDA-Approved Indications
Cephalexin is FDA-approved specifically for skin and skin structure infections caused by Staphylococcus aureus and/or Streptococcus pyogenes 2. This official indication underscores its established role as a first-line agent for these infections.
Guideline-Based Recommendations
For Non-Purulent Cellulitis and Skin Infections
The Infectious Diseases Society of America (IDSA) 2014 guidelines explicitly recommend cefalexin (cephalexin) as a first-line agent for:
- Impetigo in both pediatric and adult patients 1
- Purulent skin and soft tissue infections likely due to Staphylococcus aureus 1
- Non-purulent skin and soft tissue infections 1
- Incisional surgical site infections after surgery of the trunk or extremity 1
Clinical Efficacy Data
Cephalexin demonstrates 90-97% clinical efficacy in treating skin and soft tissue infections 3, 4. In comparative studies:
- Cephalexin achieved satisfactory clinical response in 90-95.7% of evaluable patients with skin infections 3
- When compared to other cephalosporins, cephalexin showed equivalent efficacy (89% vs 94-97% for comparators) 4
- Both twice-daily and four-times-daily dosing regimens proved equally effective (>97% efficacy) 5
When Keflex Is NOT Appropriate
Do not use cephalexin if MRSA is suspected or confirmed 1. Key indicators requiring MRSA coverage include:
- Purulent drainage with abscess formation 1
- Penetrating trauma, especially from illicit drug use 1
- Concurrent MRSA infection elsewhere 1
- Known high local MRSA prevalence 1
For MRSA coverage, switch to: vancomycin, linezolid, daptomycin, clindamycin, doxycycline, or trimethoprim-sulfamethoxazole 1
Dosing Considerations
Standard dosing is 250-500 mg orally every 6-12 hours 3, 5. The evidence supports:
- 250 mg four times daily OR 500 mg twice daily are equally effective 3, 5
- Twice-daily dosing improves compliance without sacrificing efficacy 5
- Treatment duration typically 5-14 days depending on clinical response 1
Coverage Gaps to Consider
Cephalexin has poor activity against Pasteurella multocida and should be avoided for animal bites 1. For bite wounds, use amoxicillin-clavulanate instead 1.
For dual streptococcal and MRSA coverage, combine cephalexin with either trimethoprim-sulfamethoxazole or doxycycline, as cephalexin alone does not cover MRSA 1.
Comparative Effectiveness
Meta-analysis data shows no significant difference in treatment effect between penicillins and cephalosporins for cellulitis (RR 0.99; 95% CI 0.68-1.43) 1. However, cephalexin offers the advantage of covering both staphylococci and streptococci in a single agent, whereas penicillin alone misses S. aureus 1.
Safety Profile
Cephalexin is well-tolerated with adverse events occurring in approximately 5% of patients, primarily mild gastrointestinal symptoms and skin reactions 3, 4. Drug discontinuation due to adverse effects is rare (2.3-4.95%) 3, 6.