Amoxicillin-Clavulanate Dosing for Cat Scratch Cellulitis in an 85-Year-Old
For this 85-year-old man with a one-week-old cat scratch showing redness and swelling, prescribe amoxicillin-clavulanate 875 mg/125 mg twice daily for 7-10 days. This is the standard first-line regimen recommended by the Infectious Diseases Society of America and American College of Physicians for cat scratch wounds with established infection 1, 2.
Why 875 mg Twice Daily is Preferred
The 875/125 mg twice-daily formulation is explicitly recommended in IDSA guidelines as the standard dosing for skin and soft tissue infections, including animal bite/scratch wounds 3.
This dosing provides optimal coverage against the polymicrobial flora of cat scratches, including Pasteurella multocida (75% of cat wounds), staphylococci, streptococci, and anaerobes with 100% susceptibility against P. multocida 1, 2.
The 500 mg three-times-daily formulation is not the standard recommendation in current IDSA guidelines for cellulitis or animal wounds, though it was mentioned in older comparative studies 4.
Treatment Duration and Monitoring
Complete a 7-10 day course for this uncomplicated soft tissue infection, as recommended for cat scratch wounds 1, 2.
Instruct the patient to return immediately if he develops increasing pain/redness/swelling, purulent drainage, fever, or systemic symptoms, as complications occur in approximately 18% of infected cat bite/scratch patients 1.
Special Considerations for This Elderly Patient
Age 85 requires heightened vigilance because elderly patients may have impaired immune response and are at higher risk for complications including abscess formation, bacteremia, and deep tissue involvement 1.
Monitor renal function as amoxicillin-clavulanate dosing may need adjustment if creatinine clearance is significantly reduced, though the 875 mg twice-daily formulation is generally well-tolerated 3.
Critical Distinction: Cat Scratch Wound vs. Cat Scratch Disease
This presentation (redness/swelling at one week) represents a cat scratch wound infection, not cat scratch disease (CSD), which is caused by Bartonella henselae and presents with regional lymphadenopathy 3 weeks after inoculation 2, 5.
Amoxicillin-clavulanate is appropriate for the wound infection, whereas azithromycin would be used for confirmed CSD with lymphadenopathy 2.
When to Escalate Care
If the patient fails to improve within 48-72 hours or develops systemic signs (fever, lymphangitis, confusion), consider hospitalization with IV ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1, 2.
If MRSA is suspected based on purulent drainage or local epidemiology, add trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily to the amoxicillin-clavulanate regimen 3.