What is the first-line treatment for cellulitis in a patient?

First-Line Treatment for Cellulitis

Cephalexin (500 mg orally 3-4 times daily for 5-6 days) is the first-line treatment for uncomplicated cellulitis, targeting both streptococci and methicillin-sensitive Staphylococcus aureus with cure rates of 90% or higher. 1

Pathogen Coverage and Antibiotic Selection

The most common causative organisms for cellulitis are:

• β-hemolytic Streptococcus species
• Staphylococcus aureus (methicillin-sensitive)

First-line treatment options include:

Antibiotic	Dosage	Duration
Cephalexin	500 mg 3-4 times daily	5-6 days
Amoxicillin-clavulanate	875/125 mg twice daily	5-6 days

For penicillin-allergic patients:

• Clindamycin: 300-450 mg orally three times daily for 5-6 days 1
• Doxycycline: 100 mg twice daily for 5-6 days (avoid in pregnancy and children under 8) 1

MRSA Considerations

For patients with MRSA risk factors (prior MRSA infection, frequent hospitalizations, immunocompromised status, or failed initial treatment):

• Add trimethoprim-sulfamethoxazole or
• Switch to clindamycin 1

It's important to note that even with rising rates of community-acquired MRSA, coverage for non-purulent cellulitis generally does not require MRSA coverage 2.

Treatment Duration and Monitoring

• A 5-day course of antimicrobial therapy is as effective as a 10-day course for uncomplicated cellulitis if clinical improvement occurs by day 5 1
• Patients should show improvement within 48-72 hours of starting appropriate antibiotic therapy
• If no improvement after 72 hours, consider:
  • Reevaluation of diagnosis
  • Changing antibiotic therapy
  • Possible drainage if abscess has formed 1

Special Populations

Pediatric Patients

• Cephalexin dosing: 25-50 mg/kg/day divided into 4 doses 1
• Avoid doxycycline in children under 8 years due to risk of tooth discoloration 1

Pregnant/Breastfeeding Women

• Cephalexin is generally safe during pregnancy and breastfeeding 1
• Avoid doxycycline in pregnant women in the third trimester 1

Common Pitfalls to Avoid

1. Failing to distinguish between cellulitis and pseudocellulitis (venous stasis dermatitis, contact dermatitis, eczema, lymphedema) 2
2. Unnecessary MRSA coverage in areas with low MRSA prevalence 1
3. Treating for too long (5-6 days is typically sufficient) 1
4. Failing to elevate the affected limb 1
5. Not considering underlying predisposing factors 1
6. Not performing incision and drainage for abscesses 1

Abscess Management

• Incision and drainage is the primary treatment for abscesses; antibiotics alone are insufficient 1
• Loop drainage is preferred over traditional incision and drainage technique 3
• Simple abscesses may not require antibiotics after adequate drainage 1

Remember that cellulitis is a clinical diagnosis based on history and physical examination, presenting with acute onset of redness, warmth, swelling, tenderness, and pain 2. Proper diagnosis and appropriate first-line antibiotic selection are crucial for effective treatment and preventing complications.