Is Keflex (cephalexin) effective for treating skin infections?

Effectiveness of Keflex (Cephalexin) for Skin Infections

Cephalexin (Keflex) is highly effective for treating skin and soft tissue infections, particularly those caused by Staphylococcus aureus and Streptococcus pyogenes, and is recommended as a first-line treatment option for mild skin infections by the WHO and Infectious Diseases Society of America guidelines. 1, 2

Indications and Efficacy

Cephalexin is FDA-approved for skin and skin structure infections caused by:

• Staphylococcus aureus
• Streptococcus pyogenes (Group A strep) 2

The WHO's 2024 Essential Medicines List specifically designates cephalexin as a first-choice antibiotic for:

• Mild skin and soft tissue infections
• Incisional surgical site infections after surgery of the trunk or extremities 1

Clinical Effectiveness

• Cephalexin demonstrates high efficacy with cure rates of 90% or higher for streptococcal and staphylococcal skin infections 3
• In comparative studies, cephalexin shows comparable effectiveness to other antibiotics:
  • 93.8% clinical cure rate in pediatric skin infections 4
  • 92% pathogen eradication rate in adult skin infections 5

Treatment Algorithm for Skin Infections

1. Determine infection type and severity:

   • Mild infections (impetigo, uncomplicated cellulitis, folliculitis)
   • Moderate-severe infections (extensive cellulitis, systemic symptoms)
   • Purulent vs. non-purulent infections

2. For mild to moderate non-purulent skin infections:

   • First-line: Cephalexin 500 mg orally four times daily for adults (or 25-50 mg/kg/day divided in 4 doses for children) for 5-7 days 1, 6
   • Alternative first-line options: Cloxacillin or amoxicillin-clavulanate 1

3. For purulent skin infections (likely S. aureus):

   • Consider drainage as primary intervention if abscess present
   • Cephalexin for surrounding cellulitis
   • If MRSA suspected: Switch to sulfamethoxazole-trimethoprim or clindamycin 1

4. For diabetic wound infections (mild):

   • Cephalexin is an appropriate option alongside dicloxacillin, clindamycin, or amoxicillin-clavulanate 1

Special Considerations

Dosing and Administration

• Standard adult dosing: 250-500 mg orally every 6 hours
• Treatment duration: 5-7 days for uncomplicated skin infections 6
• Dose adjustment required for patients with creatinine clearance <30 ml/min 7

Advantages

• Complete and rapid absorption in the upper intestine 7
• Achieves high tissue concentrations at infection sites
• Twice-daily dosing possible in some cases, enhancing medication compliance 3

Limitations and Precautions

• Not effective against MRSA
• Should not be used in patients with immediate (anaphylactic-type) hypersensitivity to penicillin (up to 10% cross-reactivity) 6
• Common side effects include diarrhea and gastrointestinal disturbances 4, 5

Monitoring and Follow-up

• Reassess within 48-72 hours to evaluate treatment response 6
• Consider culture and susceptibility testing if:
  • No improvement after 48-72 hours
  • Recurrent infections
  • Unusual presentation or immunocompromised host

Prevention of Recurrence

• Address predisposing conditions: edema, obesity, eczema, venous insufficiency 6
• Optimize glycemic control in diabetic patients
• Proper skin care and regular use of emollients to prevent skin dryness and cracking 6

Cephalexin remains a cornerstone antibiotic for skin infections due to its proven efficacy, favorable safety profile, and specific activity against the most common skin pathogens. While penicillin remains the drug of choice for purely streptococcal infections, cephalexin's broader coverage makes it particularly valuable for mixed or presumed staphylococcal infections.