Evaluation of Aminoglycoside Serum Concentration Monitoring

Abstract

Objectives: The primary objective of this study was to evaluate the appropriateness of when aminoglycoside serum concentrations are obtained and assess whether the timing and techniques used in obtaining aminoglycoside serum concentrations are appropriate. Additionally, pharmacists’ interpretation of aminoglycoside serum concentrations and the appropriateness of intervention in response to these results were assessed. Methods: This descriptive retrospective study to evaluate the appropriateness of aminoglycoside monitoring at an academic medical center has been approved by the Institutional Review Board. Patients over the age of 46 weeks gestational age admitted to an academic medical center between February 1, 2010 to February 1, 2011 who were prescribed intravenous aminoglycoside therapy were included in this study. Patients with therapy duration of less than 72 hours without at least one aminoglycoside level were excluded. The time of aminoglycoside concentrations in relation to time of aminoglycoside administration along with calculated pharmacokinetic parameters and therapy recommendations documented in clinical notes were also recorded. Appropriateness of aminoglycoside monitoring and documentation were determined by use of expert opinion and pharmacokinetic guidelines. Results: Timing of aminoglycoside serum concentrations and subsequent clinical assessments were evaluated in 103 subjects. The median (range) age was 28 (0.2 – 88) years. The initial aminoglycoside prescribed in 12%, 40%, and 48% of subjects was amikacin, gentamicin, and tobramycin, respectively. A total of 314 aminoglycoside concentrations were obtained: 41 amikacin, 129 gentamicin, and 144 tobramycin. At least one clinical pharmacokinetic assessment of aminoglycoside concentration(s) was written for 91 subjects (88%). The aminoglycoside indication, actual time of aminoglycoside dose administration, estimated renal function, and both goal peak/trough aminoglycoside concentrations were documented in at least one aminoglycoside clinical note for each of these 91 subjects at a rate of 95%, 80%, 89%, and 51%, respectively. Calculated peak, trough, estimated volume of distribution, and estimated half-life or ke were documented in 53 subjects. Conclusions: Aminoglycoside serum concentration monitoring can be used to maximize therapeutic outcomes while minimizing toxicity. However, errors in obtaining and evaluating serum drug levels can arise that may affect patient outcomes. For monitoring to be effective, the timing of serum concentration orders, the process of obtaining serum concentration samples, and the interpretation of data including pharmacokinetic calculations should be accurate.