Normal Vancomycin Trough Levels
For most infections, the normal vancomycin trough concentration should be 15-20 μg/mL, particularly for serious infections such as bacteremia, infective endocarditis, osteomyelitis, meningitis, pneumonia, and severe skin and soft tissue infections. 1
Trough Recommendations Based on Infection Type
Serious MRSA infections: 15-20 μg/mL 1, 2
- Bacteremia
- Infective endocarditis
- Osteomyelitis
- Meningitis
- Pneumonia
- Severe skin and soft tissue infections (e.g., necrotizing fasciitis)
Mild-moderate skin and soft tissue infections: 10-15 μg/mL 1
- For most patients with uncomplicated SSTI who have normal renal function and are not obese, traditional doses of 1 g every 12 h are adequate and trough monitoring may not be required
When to Monitor Trough Levels
Trough monitoring is recommended for: 1
- Serious infections
- Morbidly obese patients
- Patients with renal dysfunction (including those receiving dialysis)
- Patients with fluctuating volumes of distribution
Timing of Trough Measurement
- Obtain trough levels immediately before the fourth or fifth dose (at steady state) 2
- Samples should be drawn within 30 minutes before the next scheduled dose
Pharmacokinetic Considerations
The pharmacodynamic parameter that best predicts vancomycin efficacy is the ratio of the area under the curve (AUC) to the MIC (AUC/MIC). 1, 3
- Target AUC/MIC ratio: >400 1
- A trough of 15-20 μg/mL generally correlates with an AUC of approximately 400-600 μg·h/mL 1
However, it's important to note that recent evidence suggests that using trough concentrations alone may lead to inaccurate estimation of the AUC by approximately 23% compared to more robust pharmacokinetic sampling. 3 Some patients may achieve adequate AUC/MIC ratios with trough concentrations below 15 μg/mL, potentially avoiding unnecessary dose increases and associated toxicity risks. 3, 4
Special Populations
- Endocarditis: Trough levels of 15-20 μg/mL are recommended 1
- CNS infections/brain abscess: Trough levels of 15-20 μg/mL are recommended 2
Toxicity Concerns
Vancomycin-associated nephrotoxicity is associated with higher trough concentrations, particularly when:
- Troughs exceed 15-20 μg/mL
- Treatment duration is prolonged
- Patient receives concomitant nephrotoxic agents 4
Historical Context
It's worth noting that earlier recommendations (1980s-1990s) suggested lower trough targets of 5-10 μg/mL 5. However, these have been revised upward due to concerns about emerging resistance and the recognition that higher troughs are needed to achieve adequate AUC/MIC ratios for less susceptible organisms.