What is the recommended dose and duration of Vancomycin (vancomycin) for a patient with Methicillin-resistant Staphylococcus aureus (MRSA) infection, normal renal function (Glomerular Filtration Rate (GFR) > 60), and a weight of 62.7 kg?

Vancomycin Dosing for MRSA Wound Infection with Normal Renal Function

For this 62.7 kg patient with MRSA wound infection and GFR >60, administer vancomycin 1250 mg (approximately 20 mg/kg) IV every 12 hours for 7-14 days depending on wound severity and clinical response, with mandatory trough monitoring before the fourth dose targeting 15-20 μg/mL. 1, 2

Initial Dosing Strategy

Weight-based dosing is mandatory for this patient to achieve therapeutic concentrations:

• Calculate dose: 15-20 mg/kg based on actual body weight 3, 1, 4

  • For 62.7 kg: 940-1254 mg per dose
  • Round to practical dose: 1000-1250 mg IV every 12 hours 3, 4
  • Do not use fixed 1 gram doses, which systematically underdose patients and fail to achieve therapeutic targets 1, 5

• Each dose must be infused over at least 60 minutes (or 10 mg/min maximum rate, whichever is longer) to minimize infusion-related reactions 4

Loading Dose Consideration

A loading dose of 25-30 mg/kg (1565-1880 mg, rounded to 1500-2000 mg) should be administered if the wound infection is severe (necrotizing fasciitis, extensive cellulitis, or systemic signs of sepsis) 3, 1, 2:

• Loading doses enable rapid achievement of therapeutic concentrations in serious infections 1, 2
• The loading dose is not affected by renal function and should be given regardless of GFR 1
• Consider antihistamine premedication and extend infusion time to 2 hours for large loading doses to prevent red man syndrome 2, 4

For uncomplicated wound infections without systemic toxicity, proceed directly to maintenance dosing without a loading dose 3, 4

Therapeutic Monitoring Protocol

Mandatory trough level monitoring before the fourth or fifth dose (at steady state) 3, 1, 2:

• Target trough: 15-20 μg/mL for serious wound infections (deep tissue involvement, bacteremia risk) 3, 1, 2
• Target trough: 10-15 μg/mL for superficial wound infections without systemic involvement 2
• Draw trough immediately before the next scheduled dose 2
• The optimal pharmacodynamic target is AUC/MIC ratio >400, which correlates with clinical efficacy 3, 1

Duration of Therapy

Treatment duration depends on wound characteristics and clinical response 3:

• Superficial wound infections: 7-10 days if responding well clinically 3
• Deep tissue infections or abscess: 10-14 days with adequate surgical debridement 3, 6
• Complicated infections with bacteremia: 4-6 weeks of IV therapy 6
• Duration should be guided by resolution of systemic signs, wound healing, and negative repeat cultures if obtained 3

Critical Pitfalls to Avoid

Common dosing errors that lead to treatment failure:

• Never use fixed 1 gram every 12 hours dosing - this achieves therapeutic troughs in only 0-23.5% of patients with normal renal function 7, 5
• Do not target low trough levels (10-15 μg/mL) for deep or serious wound infections - this increases risk of treatment failure and resistance development 1, 2
• Avoid underdosing in patients >70 kg - 69% of patients are systematically underdosed with fixed 1 gram dosing 5

Nephrotoxicity monitoring:

• Risk increases significantly with trough levels >15 μg/mL, especially with concurrent nephrotoxic agents (aminoglycosides, piperacillin-tazobactam, NSAIDs, contrast) 2
• Monitor serum creatinine at least twice weekly during therapy 2, 4
• Consider alternative agents if multiple nephrotoxic drugs are required 2

Alternative Therapy Considerations

Switch to alternative agent if:

• Vancomycin MIC ≥2 μg/mL (VISA or VRSA) - vancomycin will fail 1, 2, 6
• Clinical failure after 48-72 hours despite adequate source control and therapeutic levels 6
• Development of nephrotoxicity with rising creatinine 2, 6

Alternative agents include:

• Daptomycin 6-10 mg/kg IV daily (not for pneumonia) 6, 8
• Linezolid 600 mg PO/IV twice daily 6, 8, 9
• Ceftaroline 600 mg IV every 12 hours 6, 9

Practical Dosing Algorithm

For this specific 62.7 kg patient:

1. If superficial wound infection without systemic signs:

   • Start 1000-1250 mg IV every 12 hours (no loading dose)
   • Target trough 10-15 μg/mL
   • Duration: 7-10 days

2. If deep wound infection or systemic signs present:

   • Give loading dose: 1500-2000 mg IV over 2 hours
   • Follow with 1250 mg IV every 12 hours
   • Target trough 15-20 μg/mL
   • Duration: 10-14 days minimum

3. Obtain trough before dose #4, adjust dosing to achieve target range 1, 2

4. Ensure adequate surgical debridement - antibiotics alone are insufficient for abscesses or necrotic tissue 3, 6