Doxycycline Dosing for Cellulitis
Doxycycline 100 mg orally twice daily for 5 days is the recommended dose for cellulitis requiring MRSA coverage, but it must be combined with a beta-lactam antibiotic because doxycycline alone lacks reliable activity against beta-hemolytic streptococci, the primary pathogen in typical cellulitis. 1
Critical Decision Point: When Doxycycline Is Appropriate
Doxycycline is indicated only for purulent cellulitis where empirical MRSA coverage is needed, specifically when these risk factors are present: 1
- Penetrating trauma or injection drug use 1
- Purulent drainage or exudate 1
- Known MRSA colonization or infection elsewhere 1
- Systemic inflammatory response syndrome (SIRS) 1
Mandatory Combination Therapy
Never use doxycycline as monotherapy for typical nonpurulent cellulitis—it must be combined with a beta-lactam such as cephalexin 500 mg four times daily or amoxicillin because tetracyclines have inadequate streptococcal coverage. 1 This combination provides coverage for both MRSA and beta-hemolytic streptococci. 1
Standard Dosing Regimen
- Adults: 100 mg orally twice daily for 5 days, extending only if clinical improvement has not occurred 1
- Children >8 years and <45 kg: 2 mg/kg/dose orally every 12 hours 1
- Children ≥8 years: May receive a 10-day course 2
Absolute Contraindications
- Children under 8 years of age: Never use doxycycline due to tooth discoloration and bone growth effects 1
- Pregnancy: Classified as pregnancy category D and should be avoided 1
When Doxycycline Is NOT Appropriate
For typical nonpurulent cellulitis without MRSA risk factors, beta-lactam monotherapy (cephalexin, dicloxacillin, or amoxicillin) is the standard of care with a 96% success rate, and adding MRSA coverage provides no additional benefit. 1 In this scenario, doxycycline is unnecessary and represents overtreatment.
Alternative Single-Agent Option
If you need both streptococcal and MRSA coverage but want to avoid combination therapy, clindamycin 300-450 mg orally four times daily is preferred as monotherapy, eliminating the need for doxycycline plus a beta-lactam. 1 However, clindamycin should only be used if local MRSA resistance rates are <10%. 1
Treatment Duration
Treat for exactly 5 days if clinical improvement occurs (reduced warmth, tenderness, and erythema). 1 Extend treatment only if the infection has not improved within this 5-day timeframe. 1 Traditional 7-14 day courses are no longer necessary for uncomplicated cases. 1
Common Pitfall to Avoid
The most frequent error is prescribing doxycycline monotherapy for typical cellulitis without purulent features—this leaves streptococci inadequately covered and leads to treatment failure. 1 Always assess whether MRSA risk factors are truly present before adding doxycycline to the regimen.