What are the dosing recommendations for cephalexin (a cephalosporin antibiotic) for uncomplicated skin and skin structure infections?

Cephalexin Dosing for Uncomplicated Skin and Skin Structure Infections

For uncomplicated skin and skin structure infections, cephalexin should be administered at 500 mg orally 3-4 times daily for 5-7 days. 1, 2

Adult Dosing

• Standard dose: 500 mg orally every 6-8 hours (3-4 times daily)
• Alternative dosing: 500 mg orally every 12 hours (twice daily) 2
• Duration: 5-7 days for uncomplicated infections 1
• Maximum daily dose: 4 grams per day 2

For streptococcal infections, treatment should be continued for a minimum of 10 days to prevent complications such as rheumatic fever 2.

Pediatric Dosing

• Standard dose: 25-50 mg/kg/day divided into 4 doses 2
• Alternative dosing: Total daily dose may be divided and administered every 12 hours 2
• Weight-based dosing guide:
  • 10 kg (22 lb): 125-250 mg (½-1 tsp of 125 mg/5 mL) four times daily
  • 20 kg (44 lb): 250-500 mg (1-2 tsp of 125 mg/5 mL) four times daily
  • 40 kg (88 lb): 500-1000 mg (2-4 tsp of 125 mg/5 mL) four times daily 2

Special Considerations

Severe Infections

• For more severe infections, dosage may be doubled 2
• If daily doses greater than 4 g are required, consider parenteral cephalosporins 2

Renal Impairment

• Dose adjustment required based on creatinine clearance 1
• Monitor renal function during treatment, especially in patients with pre-existing renal conditions

Clinical Efficacy

Cephalexin has demonstrated excellent clinical efficacy for uncomplicated skin and skin structure infections:

• Clinical cure rates of approximately 85% for uncomplicated skin infections 3
• Particularly effective against the most common pathogens in skin infections: Staphylococcus aureus and Streptococcus pyogenes 4

Alternative Agents

If cephalexin cannot be used due to allergies or other contraindications, consider:

• Clindamycin: 300-450 mg orally three times daily for 5-6 days 1
• Amoxicillin-clavulanate: 875/125 mg twice daily orally for 5-6 days 1
• Doxycycline: 100 mg twice daily 5

Common Pitfalls to Avoid

1. Inadequate duration: For streptococcal infections, treat for a full 10 days to prevent complications 2
2. Unnecessary MRSA coverage: In areas with low MRSA prevalence, broad-spectrum coverage may not be needed 1
3. Failure to address underlying factors: Identify and manage predisposing conditions like venous stasis or diabetes 1
4. Not elevating affected limb: Elevation helps reduce edema and improve healing 1

Monitoring Response

• Assess for clinical improvement within 72 hours of starting treatment 1
• Signs of improvement include decreasing erythema, warmth, swelling, and resolution of systemic symptoms 1
• If no improvement after 72 hours, consider:
  • Reevaluation of diagnosis
  • Drainage procedure if abscess present
  • Change in antibiotic therapy 1

Cephalexin remains a first-line agent for uncomplicated skin and skin structure infections due to its excellent safety profile, good tissue penetration, and efficacy against the most common causative pathogens.