Doxycycline Dosing for Cellulitis
For outpatient cellulitis requiring MRSA coverage, doxycycline should be dosed at 100 mg orally twice daily for 5 days, with extension only if clinical improvement has not occurred. 1, 2, 3
When to Use Doxycycline for Cellulitis
Purulent Cellulitis (MRSA Coverage Indicated)
- Doxycycline is appropriate for purulent cellulitis (cellulitis with purulent drainage or exudate without a drainable abscess) where empirical CA-MRSA coverage is recommended. 1
- Dose: 100 mg orally twice daily for adults. 1, 3
- Pediatric dose (>8 years, <45 kg): 2 mg/kg/dose orally every 12 hours. 1
Nonpurulent Cellulitis (Combination Therapy)
- Doxycycline must be combined with a beta-lactam (such as amoxicillin) when treating typical nonpurulent cellulitis, as tetracyclines lack reliable activity against beta-hemolytic streptococci. 1
- This combination provides dual coverage for both streptococci and CA-MRSA. 1, 2
- Beta-lactam monotherapy alone is successful in 96% of typical cellulitis cases, so doxycycline should only be added when MRSA risk factors are present. 2
Treatment Duration
- Standard duration is 5 days if clinical improvement has occurred. 2, 4
- Extend treatment beyond 5 days only if symptoms have not improved within this initial period. 1, 2
- Traditional 7-14 day courses are no longer necessary for uncomplicated cases. 2
MRSA Risk Factors Warranting Doxycycline Use
Add MRSA coverage (doxycycline) when cellulitis is associated with:
- Penetrating trauma. 2, 5
- Purulent drainage. 1, 2
- Evidence of MRSA infection elsewhere or nasal MRSA colonization. 5
- High-risk populations: athletes, prisoners, military recruits, long-term care residents, injection drug users, men who have sex with men. 6
- Failure to respond to initial beta-lactam therapy. 1
Critical Contraindications
- Never use doxycycline in children under 8 years of age due to tooth discoloration and bone growth effects. 1
- Pregnancy category D: avoid in pregnant women. 1
Common Pitfalls to Avoid
- Do not use doxycycline as monotherapy for typical nonpurulent cellulitis without adding a beta-lactam, as streptococcal coverage will be inadequate. 1
- Do not automatically add MRSA coverage for typical cellulitis without purulent features or MRSA risk factors—beta-lactam monotherapy is the standard of care. 2, 5
- Do not extend treatment beyond 5 days unless clinical improvement has failed to occur. 2, 4
- Ensure adequate dosing: inadequate weight-based dosing is independently associated with clinical failure. 7