What is a suitable first-line antibiotic for an adult patient with hand cellulitis and no known significant allergies or underlying conditions?

First-Line Antibiotic for Hand Cellulitis

For an adult with uncomplicated hand cellulitis and no significant allergies, cephalexin 500 mg orally four times daily for 5 days is the recommended first-line treatment, providing excellent coverage against streptococci and methicillin-sensitive Staphylococcus aureus, the predominant pathogens in typical cellulitis. 1

Standard Beta-Lactam Monotherapy

• Beta-lactam monotherapy is successful in 96% of patients with typical uncomplicated cellulitis, confirming that MRSA coverage is usually unnecessary. 1
• The Infectious Diseases Society of America recommends beta-lactam monotherapy as the standard of care for typical uncomplicated cellulitis, as MRSA is an uncommon cause of this condition. 1
• Recommended oral agents include cephalexin, dicloxacillin (250-500 mg every 6 hours), amoxicillin, or penicillin. 1
• Alternative options include amoxicillin-clavulanate 875/125 mg twice daily, which provides single-agent coverage for both streptococci and common skin flora. 1

Treatment Duration

• Treat for exactly 5 days if clinical improvement has occurred, extending only if symptoms have not improved within this timeframe. 1
• High-quality randomized controlled trial evidence demonstrates that 5-day courses are as effective as 10-day courses for uncomplicated cellulitis. 2
• Clinical improvement is defined as resolution of warmth and tenderness, improving erythema, and absence of fever. 1

When to Add MRSA Coverage

Do not routinely add MRSA coverage for typical hand cellulitis without specific risk factors. 1 Add MRSA-active antibiotics ONLY when these specific risk factors are present:

• Penetrating trauma or injection drug use 1
• Purulent drainage or exudate 1
• Evidence of MRSA infection elsewhere or known nasal MRSA colonization 1
• Systemic inflammatory response syndrome (SIRS): fever, tachycardia, hypotension, or altered mental status 1
• Failure to respond to beta-lactam therapy after 48-72 hours 1

MRSA Coverage Options (if indicated)

• Clindamycin 300-450 mg orally every 6 hours provides single-agent coverage for both streptococci and MRSA, avoiding the need for combination therapy. 1, 3
• Clindamycin should only be used if local MRSA clindamycin resistance rates are <10%. 1
• Alternative regimens include trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) PLUS a beta-lactam, or doxycycline (100 mg twice daily) PLUS a beta-lactam. 1
• In MRSA-prevalent areas, antibiotics without community-associated MRSA activity have 4.22 times higher odds of treatment failure (95% CI 2.25-7.92). 4

Essential Adjunctive Measures

• Elevate the affected hand above heart level to promote gravity drainage of edema and inflammatory substances, which hastens improvement. 1
• Examine interdigital spaces for tinea pedis, fissuring, scaling, or maceration, as treating these eradicates colonization and reduces recurrent infection risk. 1
• Treat predisposing conditions including edema, venous insufficiency, lymphedema, and chronic skin conditions. 1

Indications for Hospitalization

Hospitalize if any of the following are present:

• Systemic inflammatory response syndrome (SIRS), fever, hypotension, or altered mental status 1
• Severe immunocompromise or neutropenia 1
• Signs of necrotizing fasciitis: severe pain out of proportion to examination, skin anesthesia, rapid progression, gas in tissue, or bullous changes 1
• Failure of outpatient treatment after 24-48 hours 1

For hospitalized patients requiring IV therapy, cefazolin 1-2 g IV every 8 hours is the preferred IV beta-lactam. 1

Common Pitfalls to Avoid

• Do not reflexively add MRSA coverage simply because the infection involves the hand—combination therapy with trimethoprim-sulfamethoxazole plus cephalexin is no more efficacious than cephalexin alone in pure cellulitis without abscess, ulcer, or purulent drainage. 1, 5
• Do not extend treatment to 7-10 days based on residual erythema alone, as some inflammation persists even after bacterial eradication. 1
• Do not use doxycycline or trimethoprim-sulfamethoxazole as monotherapy for typical cellulitis, as their activity against beta-hemolytic streptococci is unreliable. 1
• Reassess within 24-48 hours to ensure clinical improvement; consider resistant organisms, abscess requiring drainage, or deeper infection if no improvement occurs. 1