What is the appropriate intravenous vancomycin dose and dosing interval for an adult weighing 50–70 kg with normal renal function?

Vancomycin 1g Dosing for Adults 50–70 kg with Normal Renal Function

For adults weighing 50–70 kg with normal renal function and non-severe infections, vancomycin 1 g IV every 12 hours is appropriate and does not require routine trough monitoring. 1, 2

Standard Dosing Algorithm

For Non-Severe Infections (e.g., uncomplicated cellulitis, non-complicated skin infections):

• Administer 1 g IV every 12 hours 1, 2, 3
• Infuse each dose over at least 60 minutes (minimum rate: 10 mg/min) 3
• Trough monitoring is not required for most patients with normal renal function who are not obese 1, 2

For Serious Infections (e.g., bacteremia, endocarditis, osteomyelitis, pneumonia, necrotizing fasciitis):

• Use weight-based dosing: 15–20 mg/kg every 8–12 hours 1
• For a 50 kg patient: 750 mg–1 g every 8–12 hours
• For a 70 kg patient: 1.05–1.4 g every 8–12 hours (round to 1–1.5 g)
• Consider a loading dose of 25–30 mg/kg (1.25–1.5 g for 50 kg; 1.75–2.1 g for 70 kg) for critically ill patients 1
• Target trough concentrations: 15–20 μg/mL 1
• Obtain first trough before the fourth or fifth dose 1

Infusion Guidelines

• For doses ≤1 g: Infuse over minimum 60 minutes 2, 3
• For doses >1 g: Extend infusion to 1.5–2 hours to minimize red man syndrome 1, 2
• For loading doses (25–30 mg/kg): Infuse over 2 hours with antihistamine premedication 1, 2
• Maximum concentration: 5 mg/mL (up to 10 mg/mL in fluid-restricted patients, though this increases infusion reaction risk) 3

Therapeutic Monitoring

When to Monitor:

• Mandatory monitoring: Serious infections, prolonged therapy (>3–5 days), unstable renal function, obesity, or when targeting troughs of 15–20 μg/mL 1, 2
• No routine monitoring needed: Uncomplicated skin/soft tissue infections in non-obese patients with normal renal function 1, 2

Target Concentrations:

• Non-severe infections: Trough 10–15 μg/mL 1
• Serious infections: Trough 15–20 μg/mL 1
• Pharmacodynamic goal: AUC/MIC ratio >400 1

Critical Pitfalls to Avoid

1. Underdosing obese patients: Even at 70 kg, if BMI is elevated, use actual body weight for calculations—fixed 1 g every 12 hours may be inadequate 1, 2

2. Using 1 g every 12 hours for serious infections: This traditional dose is insufficient for severe MRSA infections, bacteremia, or pneumonia 1, 4

3. Infusing too rapidly: Rates >10 mg/min or infusions <60 minutes significantly increase red man syndrome risk 3

4. Ignoring MIC values: If vancomycin MIC ≥2 μg/mL, switch to alternative agents (daptomycin, linezolid, ceftaroline) as target AUC/MIC ratios are unachievable 1

5. Failing to adjust for clinical severity: A 50 kg patient with MRSA pneumonia requires weight-based dosing (750 mg–1 g every 8 hours), not the standard 1 g every 12 hours 1, 4

Special Considerations

• Critically ill patients: Always use loading dose of 25–30 mg/kg regardless of renal function, as volume of distribution is expanded due to fluid resuscitation 1
• MRSA pneumonia: Consider linezolid as first-line due to superior lung penetration and better outcomes compared to vancomycin 1
• Nephrotoxicity risk: Increases significantly with troughs >15 μg/mL, especially with concurrent nephrotoxic agents (aminoglycosides, piperacillin-tazobactam, NSAIDs) 1