How often should vancomycin trough levels be checked?

Vancomycin Trough Monitoring Frequency

Obtain the initial vancomycin trough level before the fourth or fifth dose (at steady state), and continue monitoring frequency based on infection severity, renal function, and patient risk factors. 1

Initial Trough Monitoring

• Draw the first trough level prior to the fourth or fifth dose to ensure steady-state conditions have been reached 1
• Pre-dose (trough) monitoring is the most accurate and practical method for guiding vancomycin dosing 1
• Peak vancomycin concentration monitoring is not recommended and provides limited clinical value 1, 2, 3

Ongoing Monitoring Frequency

For Serious Infections Requiring Monitoring:

• Serious infections (bacteremia, endocarditis, osteomyelitis, meningitis, pneumonia, severe skin/soft tissue infections) require trough monitoring with target levels of 15-20 mg/L 1
• After any dose adjustment, measure a new trough level before the fourth or fifth dose at the new steady state 2
• Monitor serum creatinine closely throughout therapy for nephrotoxicity (defined as ≥2-3 consecutive increases in creatinine of 0.5 mg/dL or 150% increase from baseline) 2, 3

High-Risk Patients Requiring More Frequent Monitoring:

Trough monitoring is mandatory for 1:

• Patients with morbid obesity
• Patients with renal dysfunction (including those on dialysis)
• Patients with fluctuating volumes of distribution
• Patients receiving treatment duration >7 days (increased nephrotoxicity risk) 4

Patients NOT Requiring Routine Trough Monitoring:

• Most skin/soft tissue infections in patients with normal renal function who are not obese can be treated with traditional doses (1 g every 12 hours) without trough monitoring 1

Management of Abnormal Levels

When Trough Exceeds 20 mg/L:

• Hold the next scheduled dose immediately 2, 3
• Recheck trough level before administering any subsequent doses 2, 3
• Once levels decrease to target range (15-20 mg/L for serious infections), resume at reduced dose (approximately 15-20% reduction) or extended dosing interval 2, 3
• Sustained trough concentrations >20 μg/mL significantly increase nephrotoxicity risk 2, 3, 5

When Levels Are Subtherapeutic:

• For serious infections with MIC ≤1 mg/L, target AUC/MIC ratio ≥400 3
• Consider loading dose of 25-30 mg/kg (actual body weight) in critically ill patients with sepsis, meningitis, pneumonia, or endocarditis to rapidly achieve therapeutic levels 1

Critical Pitfalls to Avoid

• Never continue the same dosage despite elevated trough levels >20 mg/L, as this substantially increases nephrotoxicity risk 2, 3
• Never rely solely on nomograms—individual pharmacokinetic adjustments are necessary 3
• Never discontinue vancomycin completely when still clinically indicated; instead, adjust the dose appropriately 2, 3
• Never use vancomycin when MIC ≥2 mg/L (VISA/VRSA), as target AUC/MIC ratios are not achievable—switch to alternative therapy 1, 3
• Treatment duration >7 days with high trough levels shows a linear relationship with increased nephrotoxicity risk 4