Is Keflex (cephalexin) effective for treating skin infections?

Cephalexin for Skin Infections

Cephalexin is highly effective for treating skin and soft tissue infections, particularly those caused by streptococci and methicillin-susceptible Staphylococcus aureus (MSSA), and is recommended as a first-line treatment option by current guidelines. 1

Efficacy and Indications

Cephalexin demonstrates excellent efficacy against common skin pathogens:

• FDA-approved specifically for skin and skin structure infections caused by Staphylococcus aureus and Streptococcus pyogenes 2
• Recommended as a first-line agent for mild skin infections by the WHO's Essential Medicines List 1
• The Infectious Diseases Society of America (IDSA) recommends cephalexin for non-purulent cellulitis and surgical site infections 1
• Clinical cure rates of 90% or higher have been consistently achieved 3

Treatment Algorithm for Skin Infections

1. For mild non-purulent skin infections (typical cellulitis/erysipelas):

   • Cephalexin 500 mg orally four times daily for 5-7 days 1, 4
   • Alternative options: dicloxacillin, amoxicillin-clavulanate, or cloxacillin 1

2. For purulent skin infections:

   • Incision and drainage is the primary treatment
   • If antibiotics needed: cephalexin if MRSA is not suspected 1
   • If MRSA suspected: trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 1

3. For surgical site infections (trunk or extremity away from axilla/perineum):

   • Cephalexin is recommended as an appropriate option 1

4. For diabetic wound infections (mild):

   • Cephalexin is among the recommended options 1

Advantages of Cephalexin

• Excellent oral bioavailability (not absorbed from stomach but totally and rapidly absorbed in upper intestine) 5
• Stability and chemical configuration result in very low incidence of allergic reactions 5
• Twice-daily dosing possible, enhancing medication compliance 3
• Available in suspension form for pediatric patients 3

Limitations and Considerations

• Not effective against MRSA - alternative coverage should be considered if MRSA is suspected 4
• Up to 10% of penicillin-allergic patients may also be allergic to cephalosporins 4
• Should not be used in patients with immediate (anaphylactic-type) hypersensitivity to penicillin 4
• Dose adjustment required for patients with creatinine clearance less than 30 ml/min 5

Comparative Efficacy

• Cephalexin (500 mg twice daily) showed 89% clinical success rate in treating skin infections, comparable to other cephalosporins 6
• Equivalent clinical efficacy to ofloxacin for skin and soft tissue infections (83.6% cure rate for cephalexin vs. 85.2% for ofloxacin) 7
• Similar efficacy to cefdinir but with fewer adverse effects (16% vs. 26% adverse reaction rate) 8

Monitoring and Follow-up

• Reevaluate patients within 48-72 hours to assess treatment response 4
• Consider hospitalization if no improvement within 24-48 hours of outpatient treatment 4
• Cultures should be obtained before initiating antibiotic therapy when possible 4

Prevention of Recurrence

• Address predisposing factors such as edema, obesity, eczema, and venous insufficiency 4
• Consider prophylactic antibiotics for patients with 3-4 episodes of cellulitis per year 4

Cephalexin remains a cornerstone antibiotic for skin and soft tissue infections due to its proven efficacy, safety profile, and specific activity against the most common causative pathogens. Its inclusion as a first-choice antibiotic in the WHO Essential Medicines List underscores its continued importance in treating these common infections.