Doxycycline Dosing for Cellulitis
For cellulitis requiring MRSA coverage, doxycycline should be dosed at 100 mg orally twice daily for 5 days, but it must always be combined with a beta-lactam antibiotic because doxycycline lacks reliable activity against beta-hemolytic streptococci, which are the primary pathogens in typical cellulitis. 1
When Doxycycline is Appropriate
Doxycycline is indicated only for specific cellulitis presentations requiring empirical MRSA coverage, including: 1
- Purulent cellulitis with drainage or exudate 1
- Penetrating trauma or injection drug use 1
- Known MRSA colonization or infection elsewhere 1
- Systemic inflammatory response syndrome (SIRS) 1
- Failure of initial beta-lactam therapy 1
Critical Dosing Details
Adult Dosing
- Standard dose: 100 mg orally every 12 hours 1, 2
- Loading dose: 200 mg on day 1 (administered as 100 mg every 12 hours), followed by 100 mg twice daily 2
- Duration: 5 days if clinical improvement occurs; extend only if symptoms have not improved 1
Pediatric Dosing
- Children >8 years and <45 kg: 2 mg/kg/dose orally every 12 hours 1
- Children >100 lb: Use adult dose 2
- Never use in children <8 years due to tooth discoloration and bone growth effects 1
Mandatory Combination Therapy
Doxycycline monotherapy is inadequate for typical cellulitis. 1 You must combine it with a beta-lactam to ensure streptococcal coverage: 1
- Doxycycline 100 mg twice daily PLUS cephalexin 500 mg four times daily 1
- Doxycycline 100 mg twice daily PLUS amoxicillin 500 mg three times daily 1
- Alternative: Clindamycin 300-450 mg every 6 hours as monotherapy (covers both streptococci and MRSA, avoiding need for combination) 1
Common Pitfalls to Avoid
- Never use doxycycline alone for nonpurulent cellulitis without adding a beta-lactam, as streptococcal coverage will be inadequate 1
- Avoid in pregnancy (category D) 1
- Do not exceed recommended dosing, as this increases side effects without improving efficacy 2
- Administer with adequate fluids to reduce risk of esophageal irritation and ulceration 2
- May give with food or milk if gastric irritation occurs, as absorption is not significantly affected 2
When Doxycycline is NOT Appropriate
For typical nonpurulent cellulitis (the vast majority of cases), beta-lactam monotherapy is the standard of care with a 96% success rate, and MRSA coverage is unnecessary: 1
- Preferred agents: Cephalexin, dicloxacillin, amoxicillin, or penicillin 1
- Duration: 5 days if clinical improvement occurs 1