Antibiotic Treatment for Infected Finger Cut with Cellulitis
For an infected finger cut with swelling, heat, and red streaks (lymphangitis), start oral cephalexin 500 mg four times daily or dicloxacillin 500 mg four times daily for 5 days, as these beta-lactam antibiotics provide excellent coverage against the most common pathogens (β-hemolytic streptococci and methicillin-sensitive Staphylococcus aureus) and are successful in 96% of typical cellulitis cases. 1
First-Line Treatment Approach
Beta-lactam monotherapy is the standard of care for typical uncomplicated cellulitis, even with red streaks indicating lymphangitic spread. 1
Recommended oral agents include:
Treatment duration is 5 days if clinical improvement occurs, extending only if symptoms have not improved within this timeframe. 1
MRSA coverage is NOT routinely necessary for typical nonpurulent cellulitis, as MRSA is an uncommon cause even in high-prevalence settings, with beta-lactam success rates of 96%. 1, 4
When to Add MRSA Coverage
Add MRSA-active antibiotics ONLY when specific risk factors are present: 1
- Penetrating trauma (such as a puncture wound or deep laceration) 1
- Purulent drainage or exudate from the wound 1
- Injection drug use 1
- Known MRSA colonization or evidence of MRSA infection elsewhere 1
- Systemic inflammatory response syndrome (SIRS) with fever, tachycardia, or altered mental status 1
If MRSA coverage is needed, use: 1
- Clindamycin 300-450 mg orally every 6 hours (covers both streptococci and MRSA as monotherapy) 1, 5
- Trimethoprim-sulfamethoxazole PLUS a beta-lactam (combination required because TMP-SMX lacks reliable streptococcal coverage) 1
- Doxycycline 100 mg twice daily PLUS a beta-lactam (combination required because doxycycline lacks reliable streptococcal coverage) 1
Special Circumstances
If Penicillin Allergic:
- Clindamycin 300-450 mg orally every 6 hours is the optimal choice, providing single-agent coverage for both streptococci and MRSA without requiring combination therapy. 1, 5
- Use clindamycin only if local MRSA clindamycin resistance rates are <10%. 1
If Bite-Related (Human or Animal):
- Amoxicillin-clavulanate (Augmentin) 875/125 mg twice daily provides single-agent coverage for polymicrobial oral flora. 1
Critical Warning Signs Requiring Hospitalization
Seek immediate medical attention if any of the following develop: 1
- Severe pain out of proportion to examination (suggests necrotizing fasciitis)
- Rapid progression despite antibiotics within 24-48 hours
- Systemic toxicity: fever >38°C, hypotension, tachycardia >90 bpm, altered mental status
- Skin anesthesia, bullous changes, or gas in tissue
- Severe immunocompromise or neutropenia
For severe infections requiring hospitalization, IV vancomycin 15-20 mg/kg every 8-12 hours PLUS piperacillin-tazobactam 3.375-4.5 g every 6 hours is recommended. 1
Adjunctive Measures
- Elevate the affected hand above heart level to promote gravitational drainage of edema and hasten improvement. 1
- Reassess in 24-48 hours to verify clinical response, as treatment failure rates of 21% have been reported with some regimens. 1
- Mark the borders of erythema with a pen to objectively track progression or improvement. 1
Common Pitfalls to Avoid
- Do NOT routinely add MRSA coverage for typical nonpurulent cellulitis without specific risk factors—this represents overtreatment and increases antibiotic resistance. 1
- Do NOT use doxycycline or TMP-SMX as monotherapy for cellulitis, as their activity against β-hemolytic streptococci is unreliable. 1
- Do NOT continue ineffective antibiotics beyond 48 hours—progression despite appropriate therapy indicates either resistant organisms or a deeper/different infection. 1
- Do NOT assume purulent drainage—if fluctuance is present, incision and drainage is the primary treatment, not antibiotics alone. 1