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Pitfalls in dosing vancomycin
Sireesha Koppula1, Shivani Ruben, Farhan Bangash
1Department of Medicine, College of Medicine, University of Arizona, Tucson, Arizona.
Background:
Vancomycin is a frequently used antibiotic for the treatment of methicillin-resistant gram-positive bacteria. Newer guidelines suggest dosing vancomycin to achieve a trough concentration between 15 and 20 mg/L. Achieving this higher concentration requires greater doses of the antibiotic. Even when using a nomogram, these higher doses often result in excessively elevated trough levels and increase the risk for vancomycin-associated acute kidney injury. We undertook this quality improvement project to better understand the reasons contributing to a toxic vancomycin trough level.
Methods:
Over a 9-month period, we examined all vancomycin trough concentrations greater than 25 mg/L to determine their cause.
Results:
Fifty-four elevated levels were identified in 38 patients. In 47 instances, adequate data were available for analysis. We could classify the etiology of the excessive levels into 4 groups: (1) incorrect timing of the blood collection, (2) improper dosing, (3) changing renal function and (4) abnormal pharmacokinetics/pharmacodynamics.
Conclusions:
Educational programs could correct the first 3 problems. However, only more frequent therapeutic drug monitoring or use of another, less toxic, antibiotic would remedy the last one.
Insights
Higher vancomycin doses increase toxicity risk. This study identified incorrect timing, dosing, renal function changes, and abnormal pharmacokinetics as key reasons for toxic vancomycin levels.
Area of Science:
- Pharmacology
- Nephrology
- Infectious Diseases
Background:
- Vancomycin is crucial for treating methicillin-resistant gram-positive bacteria.
- Newer guidelines recommend higher vancomycin trough concentrations (15-20 mg/L).
- Higher doses increase the risk of vancomycin-associated acute kidney injury.
Purpose of the Study:
- To investigate the causes of toxic vancomycin trough levels.
- To identify factors contributing to excessively high vancomycin concentrations.
- To inform strategies for safer vancomycin dosing.
Main Methods:
- A 9-month quality improvement project.
- Analysis of vancomycin trough concentrations > 25 mg/L.
- Classification of etiological factors for elevated levels.
Main Results:
- Fifty-four elevated levels identified in 38 patients.
- Etiologies included incorrect blood collection timing, improper dosing, changing renal function, and abnormal pharmacokinetics/pharmacodynamics.
- Forty-seven instances had adequate data for analysis.
Conclusions:
- Educational interventions can address timing, dosing, and renal function issues.
- Abnormal pharmacokinetics/pharmacodynamics require more frequent therapeutic drug monitoring or alternative antibiotics.
- Strategies are needed to mitigate risks associated with higher vancomycin doses.
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