Levofloxacin Dosing for Staphylococcus aureus Wound Infection in an Elderly Female
For an elderly female patient with a susceptible Staphylococcus aureus wound infection, levofloxacin 750 mg once daily is the recommended dosage. 1
Rationale for 750 mg Daily Dosing
The 2014 IDSA Skin and Soft Tissue Infection Guidelines specifically list levofloxacin 750 mg daily as the appropriate dosing for skin and soft tissue infections in adults. 1 This higher dose is preferred over the standard 500 mg dose for several important reasons:
- Enhanced bactericidal activity: The 750 mg dose maximizes levofloxacin's concentration-dependent killing against Staphylococcus aureus 2
- Better tissue penetration: Higher doses achieve more reliable drug concentrations at the wound site 3, 4
- Reduced resistance potential: The higher dose helps prevent the emergence of resistant organisms 2
Special Considerations for Elderly Patients
Elderly patients actually achieve higher drug exposure with levofloxacin compared to younger patients, which works in favor of efficacy but requires monitoring. 5 Specifically:
- Elderly patients have reduced levofloxacin clearance and longer half-life (9.8 hours vs 7.4 hours in younger patients) 5
- This results in higher AUC/MIC ratios, improving bacterial eradication 5
- The 750 mg dose provides >98% probability of achieving pharmacodynamic targets in elderly patients 5
Duration of Therapy
Treatment duration should be 7-10 days for uncomplicated skin infections, though this may be extended if clinical improvement is inadequate. 1 The guidelines emphasize that:
- Staphylococcus aureus infections may require longer treatment courses than streptococcal infections 1
- Treatment should continue until signs of active infection have resolved 1
Important Caveats
Levofloxacin is NOT a first-line agent for Staphylococcus aureus skin infections. 1 The IDSA guidelines clearly recommend:
- Preferred agents for MSSA: Nafcillin, oxacillin, cefazolin, or dicloxacillin 1
- Preferred agents for MRSA: Vancomycin, linezolid, daptomycin, or ceftaroline 1
- Fluoroquinolones are listed as alternatives, primarily for bite wounds or mixed infections 1
Critical warning: If this is MRSA rather than methicillin-susceptible S. aureus, levofloxacin monotherapy is inadequate and inappropriate. 1 The susceptibility testing must confirm activity against the specific isolate, as fluoroquinolone resistance in S. aureus can be significant in certain geographic areas. 1
Renal Dose Adjustment
Elderly patients frequently have reduced renal function, which necessitates dose adjustment. While the evidence provided doesn't specify exact adjustments, standard practice requires checking creatinine clearance and adjusting accordingly, as levofloxacin is renally eliminated. 3