What is the recommended dosage of doxycycline (Doxycycline) for the treatment of cellulitis?

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

Critical Decision Point: When to Use Doxycycline

Doxycycline is appropriate only when specific MRSA risk factors are present 1:

• Purulent drainage or exudate from the cellulitis site 1
• Penetrating trauma or injection drug use 1
• Known MRSA colonization or evidence of MRSA infection elsewhere 1
• Systemic inflammatory response syndrome (SIRS) 1

For typical nonpurulent cellulitis without these risk factors, beta-lactam monotherapy (such as cephalexin 500 mg four times daily) is the standard of care and is successful in 96% of patients—doxycycline should NOT be used. 1, 2

Specific Dosing Regimen

Adult Dosing

• Doxycycline: 100 mg orally twice daily (every 12 hours) 1, 3
• PLUS a beta-lactam: cephalexin 500 mg four times daily OR dicloxacillin 250-500 mg every 6 hours 1, 2
• Duration: 5 days if clinical improvement occurs; extend only if symptoms have not improved 1, 3

Pediatric Dosing (Children >8 years)

• 2 mg/kg/dose orally every 12 hours for children weighing less than 45 kg 1
• For children over 100 pounds, use the adult dose of 100 mg twice daily 3

Why Combination Therapy is Mandatory

Doxycycline as monotherapy for cellulitis is inadequate and should never be used alone. 1 Here's why:

• Beta-hemolytic streptococci (primarily Streptococcus pyogenes) cause the majority of typical cellulitis cases 1
• Doxycycline has unreliable activity against these streptococcal pathogens 1
• The beta-lactam component provides essential streptococcal coverage while doxycycline covers potential MRSA 1

Alternative to Combination Therapy

If you want to avoid combination therapy, use clindamycin 300-450 mg orally every 6 hours as monotherapy—it covers both streptococci and MRSA, eliminating the need for two separate antibiotics. 1 However, this is only appropriate if local MRSA clindamycin resistance rates are less than 10% 1.

Absolute Contraindications

• Never use doxycycline in children under 8 years of age due to permanent tooth discoloration and impaired bone growth 1
• Avoid in pregnant women (pregnancy category D) 1

Common Pitfalls to Avoid

• Do not prescribe doxycycline alone for cellulitis—this is the most common error and will result in treatment failure due to inadequate streptococcal coverage 1
• Do not add MRSA coverage reflexively—if the cellulitis is nonpurulent without specific risk factors, beta-lactam monotherapy is superior and avoids unnecessary antibiotic exposure 1
• Do not extend treatment beyond 5 days automatically—traditional 7-14 day courses are outdated for uncomplicated cases 1, 4

Adjunctive Measures

• Elevate the affected extremity to promote drainage and hasten improvement 1
• Examine and treat interdigital toe spaces for tinea pedis, as this reduces recurrence risk 1
• Address predisposing conditions including venous insufficiency, lymphedema, and chronic edema 1