In an adult without a penicillin allergy who has a mild‑to‑moderate cellulitis or superficial abscess of the foot, is amoxicillin‑clavulanate (Augmentin) appropriate and what oral dosing regimen should be used, including adjustments for impaired renal function?

Amoxicillin-Clavulanate (Augmentin) for Mild-to-Moderate Foot Cellulitis

Amoxicillin-clavulanate 875/125 mg orally twice daily for 5 days is appropriate for mild-to-moderate foot cellulitis in adults without penicillin allergy, but only when the infection is associated with human or animal bites, open wounds with environmental contamination, or when broader polymicrobial coverage is specifically needed. For typical non-purulent foot cellulitis without these features, beta-lactam monotherapy with cephalexin or dicloxacillin is preferred and achieves approximately 96% clinical success. 1

When Augmentin Is Appropriate vs. Standard Beta-Lactams

Use Augmentin (875/125 mg twice daily) when:

• Bite-related cellulitis (human or animal) is present, as it provides single-agent coverage for polymicrobial oral flora including anaerobes 1
• Open wounds with environmental contamination exist, requiring coverage of gram-negative and anaerobic organisms introduced through the puncture 1
• Diabetic foot infections (mild-to-moderate severity) are present, where polymicrobial coverage is needed 2, 3

Use standard beta-lactams (cephalexin 500 mg q6h or dicloxacillin 250-500 mg q6h) when:

• Typical non-purulent cellulitis without drainage, trauma, or bite history is present 1, 4
• The patient has no MRSA risk factors (no penetrating trauma, injection drug use, purulent drainage, known MRSA colonization, or SIRS) 1, 4
• Beta-lactam monotherapy achieves 96% success because the primary pathogens are beta-hemolytic streptococci and methicillin-sensitive Staphylococcus aureus 1

Standard Dosing Regimen

• Amoxicillin-clavulanate 875/125 mg orally twice daily for 5 days if clinical improvement (reduced warmth, tenderness, erythema; afebrile) occurs 1
• Extend treatment only if symptoms have not improved after the initial 5-day course; traditional 7-14 day regimens are unnecessary for uncomplicated cases 1
• High-quality randomized controlled trial evidence shows 5-day courses are as effective as 10-day courses, achieving 98% clinical resolution at 14 days 1

High-Dose Regimen for Resistant Organisms

• Amoxicillin-clavulanate 2000/125 mg twice daily can be considered for patients failing standard therapy or in regions with high antibiotic resistance, achieving higher serum concentrations to overcome organisms with elevated MICs 1

Renal Dose Adjustments

For GFR 30-59 mL/min:

• No dose adjustment needed for standard 875/125 mg twice daily regimen 1
• Most oral antibiotics for cellulitis require no modification at this level of renal function 1

For GFR 10-30 mL/min:

• Reduce to 875/125 mg once daily or 500/125 mg twice daily 5

For GFR <10 mL/min or hemodialysis:

• 500/125 mg once daily on non-dialysis days 5
• 500/125 mg after each dialysis session, as both amoxicillin and clavulanate are significantly removed by hemodialysis (fractional removal 0.64-0.65) 5
• Dialysis clearance for amoxicillin is 77.1 mL/min and for clavulanate is 92.8 mL/min 5

When to Add MRSA Coverage Instead

Do not use Augmentin when MRSA risk factors are present; switch to MRSA-active agents: 1, 4

MRSA Risk Factors Requiring Alternative Therapy:

• Penetrating trauma or injection drug use 1, 4
• Visible purulent drainage or exudate 1, 4
• Known MRSA colonization or prior MRSA infection 1
• Systemic inflammatory response syndrome (fever >38°C, HR >90, RR >24) 1, 4
• Failure to respond to beta-lactam therapy after 48-72 hours 1

MRSA-Active Regimens (when risk factors present):

• Clindamycin 300-450 mg orally every 6 hours provides single-agent coverage for both streptococci and MRSA, but use only if local clindamycin resistance <10% 1, 4, 3
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily PLUS a beta-lactam (cephalexin or amoxicillin) to ensure streptococcal coverage 1, 4
• Doxycycline 100 mg twice daily PLUS a beta-lactam for dual coverage 1, 4

Special Considerations for Diabetic Foot Infections

Diabetic foot cellulitis requires broader and longer treatment than simple cellulitis: 2, 3

Mild Diabetic Foot Infections:

• Amoxicillin-clavulanate 875/125 mg twice daily is appropriate 2, 3
• Alternative options include levofloxacin, trimethoprim-sulfamethoxazole, or clindamycin 2
• Duration typically 1-2 weeks, longer than the 5 days used for simple cellulitis 2

Moderate Diabetic Foot Infections:

• Consider IV therapy with ceftriaxone, ampicillin-sulbactam, or ertapenem 2
• Oral step-down to amoxicillin-clavulanate 875/125 mg twice daily is acceptable once improved 2

Severe Diabetic Foot Infections:

• Require IV piperacillin-tazobactam, imipenem-cilastatin, or vancomycin plus ceftazidime 2
• Duration 2-4 weeks depending on structures involved and adequacy of debridement 2

Essential Adjunctive Measures

• Elevate the affected foot above heart level for at least 30 minutes three times daily to promote venous drainage 1, 4
• Examine interdigital toe spaces for tinea pedis, fissuring, scaling, or maceration; treating these reduces recurrent cellulitis by up to 50% 1, 4
• Apply topical antifungals (clotrimazole, terbinafine) to eradicate tinea pedis and eliminate bacterial portal of entry 4
• Address predisposing conditions including venous insufficiency, lymphedema, chronic edema, and obesity 1, 4
• Optimize glycemic control in diabetic patients, as this aids infection eradication and wound healing 3

Hospitalization Criteria and IV Therapy

Admit patients with foot cellulitis when any of the following are present: 1, 4

• Systemic inflammatory response syndrome (fever, hypotension, tachycardia, altered mental status) 1, 4
• Signs of necrotizing infection (severe pain out of proportion, skin anesthesia, rapid progression, "wooden-hard" tissue) 1, 4
• Severe immunocompromise or neutropenia 1
• Failure of outpatient therapy after 24-48 hours 1

IV Regimens for Hospitalized Patients:

• Without MRSA risk: cefazolin 1-2 g IV every 8 hours 1, 4
• With MRSA risk: vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mg/L) 1, 4
• Severe cellulitis with systemic toxicity: vancomycin PLUS piperacillin-tazobactam 3.375-4.5 g IV every 6 hours for 7-10 days 1, 4

Critical Pitfalls to Avoid

• Do not use Augmentin for typical non-purulent foot cellulitis without bite history or open wounds; cephalexin or dicloxacillin achieves 96% success and avoids unnecessary broad-spectrum coverage 1
• Do not add MRSA coverage routinely for typical cellulitis without the specified risk factors; MRSA is uncommon even in high-prevalence settings 1, 4
• Do not automatically extend therapy to 7-10 days based solely on residual erythema; extend only if warmth, tenderness, or erythema have not improved after 5 days 1
• Do not store Augmentin in hot environments (e.g., car in summer), as high temperatures accelerate drug breakdown and reduce effectiveness 6
• Do not use Augmentin alone for severe diabetic foot infections; these require IV broad-spectrum therapy initially 2

Follow-Up and Monitoring

• Reassess within 24-48 hours to verify clinical response; treatment failure rates of approximately 21% have been reported with some oral regimens 1, 4
• If no improvement after 48-72 hours, consider resistant organisms, undrained abscess, deeper infection (osteomyelitis, septic arthritis), or alternative diagnoses 1
• Document the area of erythema at baseline and follow-up to objectively track progression or improvement 1