What is the recommended dose of vancomycin for a patient with Methicillin-resistant Staphylococcus aureus (MRSA) infection weighing 62.7kg, given 15mg/kg?

Vancomycin Dosing Calculation for MRSA Infection

For a 62.7 kg patient with MRSA infection, the calculated dose is 940.5 mg per dose (15 mg/kg × 62.7 kg), which should be administered every 6-12 hours depending on infection severity and site. 1, 2

Dose Calculation and Administration

The standard weight-based dosing for MRSA infections is 15-20 mg/kg per dose based on actual body weight:

• For this 62.7 kg patient:

  • Minimum dose: 15 mg/kg × 62.7 kg = 940.5 mg per dose 1, 2
  • Maximum dose: 20 mg/kg × 62.7 kg = 1,254 mg per dose 1, 2
  • Do not exceed 2 g per single dose 2, 3

• Dosing frequency depends on infection severity: 1

  • Serious infections (bacteremia, endocarditis, pneumonia, meningitis, osteomyelitis): 15 mg/kg IV every 6 hours 1
  • Less severe infections: 15 mg/kg IV every 8-12 hours 1, 3

• Infusion rate is critical to prevent adverse reactions: 3

  • Administer at no more than 10 mg/min 3
  • Each dose must infuse over at least 60 minutes, whichever is longer 3
  • For a 940 mg dose, this equals a 94-minute minimum infusion time 3

Loading Dose Considerations

For seriously ill patients with sepsis, pneumonia, meningitis, or endocarditis, consider a loading dose:

• 25-30 mg/kg loading dose (1,567.5 - 1,881 mg for this patient) 2, 4
• This rapidly achieves therapeutic concentrations in critically ill patients with expanded volumes of distribution 2, 4
• Prolong infusion to 2 hours and consider antihistamine premedication to prevent red man syndrome 4

Therapeutic Monitoring Requirements

Target trough concentrations of 15-20 μg/mL are essential for serious MRSA infections:

• Obtain first trough level before the fourth or fifth dose at steady state 2, 4
• The AUC/MIC ratio >400 is the pharmacodynamic parameter that best predicts efficacy 1, 2
• Trough monitoring is mandatory for this patient if they have serious infection, renal dysfunction, obesity, or fluctuating volume status 1, 2

Common Pitfalls to Avoid

The traditional "1 gram every 12 hours" dosing is inadequate for most patients:

• Studies show 69% of patients are underdosed with fixed 1 g dosing 5
• Weight-based dosing is particularly critical—this 62.7 kg patient requires approximately 940 mg per dose, not the standard 1 g 1, 5
• Underdosing leads to treatment failure and promotes resistance development 4, 5

For isolates with vancomycin MIC ≥2 μg/mL, switch to an alternative agent:

• Target AUC/MIC ratios are not achievable with conventional vancomycin dosing 2, 4
• Alternative agents include daptomycin 6-10 mg/kg IV daily, linezolid 600 mg IV/PO q12h, or TMP-SMX 1, 2, 6

Renal Function Adjustments

If this patient has renal impairment, dosing must be adjusted:

• The initial dose should still be at least 15 mg/kg even with mild-moderate renal insufficiency 3
• Subsequent doses are adjusted based on creatinine clearance 3
• Trough monitoring becomes even more critical in renal dysfunction 1, 6