What is the initial treatment for Cellulitis?

Initial Treatment for Cellulitis

For uncomplicated cellulitis, the initial treatment is oral cephalexin 500 mg 3-4 times daily for 5-6 days. 1

First-Line Antibiotic Options

The choice of initial antibiotic therapy should be guided by the likely causative organisms and local resistance patterns:

• Standard first-line options (for mild to moderate uncomplicated cellulitis):

  • Cephalexin: 500 mg 3-4 times daily for 5-6 days 1
  • Dicloxacillin: 250-500 mg every 6 hours (125 mg every 6 hours for mild cases) 2
  • Clindamycin: 300-450 mg three times daily for 5-6 days (for penicillin-allergic patients) 1, 3

• When MRSA is suspected (previous MRSA infection, injection drug use, SIRS, failed initial treatment, or immunocompromised status):

  • Doxycycline: 100 mg twice daily for 5-6 days 1
  • Trimethoprim-sulfamethoxazole plus clindamycin (particularly in HIV-positive individuals with cellulitis related to injection drug use) 1
  • Clindamycin: 300-450 mg three times daily 1, 3

Treatment Duration

• Standard duration for uncomplicated cellulitis: 5-7 days 1
• More severe infections or slow clinical response: 10-14 days 1
• Continue treatment until the patient is afebrile and asymptomatic for at least 48 hours 1, 2

Special Considerations

Severity Assessment

• Mild to moderate: Localized infection with minimal systemic symptoms → oral antibiotics
• Severe: Extensive involvement, systemic symptoms, immunocompromised host → consider intravenous therapy with vancomycin (15-20 mg/kg IV every 8-12 hours) 1

Important Cautions

• Doxycycline should be avoided in:

  • Children under 8 years (risk of tooth discoloration)
  • Pregnant women in the third trimester
  • Infants younger than 2 months 1

• Dicloxacillin administration:

  • Take on an empty stomach (1 hour before or 2 hours after meals)
  • With at least 4 fluid ounces (120 mL) of water
  • Not in the supine position or immediately before bed 2

• Clindamycin warning:

  • Discontinue if significant diarrhea occurs (risk of C. difficile infection) 3

Monitoring and Reassessment

• Reassess within 48-72 hours to ensure clinical improvement 1
• If no improvement, consider:
  1. Broadening antibiotic coverage
  2. Evaluating for possible abscess requiring drainage
  3. Investigating underlying conditions affecting treatment response 1

Common Pitfalls to Avoid

• Failing to consider local resistance patterns when selecting empiric therapy 1
• Not providing adequate duration of therapy for deep-seated infections 1, 2
• Overlooking the possibility of an abscess requiring drainage in addition to antibiotics 1
• Misdiagnosing conditions that mimic cellulitis (venous stasis dermatitis, contact dermatitis, deep vein thrombosis) 4, 5, 6
• Not adjusting therapy when initial treatment fails (consider unusual pathogens like P. mirabilis in such cases) 7

Remember that while β-hemolytic Streptococcus and methicillin-sensitive S. aureus are the most common causative organisms, the majority of cellulitis cases are nonculturable, making empiric therapy based on likely pathogens essential 4, 6.