gms | German Medical Science

Vancomycin is a well-established treatment for methicillin-resistant Staphylococcus aureus infections (MRSA). In order to maximize therapeutic effect and to reduce toxicity (e.g. nephrotoxicity) therapeutic drug monitoring (TDM) of vancomycin is recommended. While for several years a vancomycin trough level of 5–10 mg/l was considered adequate, in 2009 a revised practice guideline [1] was released addressing the trend of higher vancomycin MIC and therefore the need of higher vancomycin exposure (vancomycin trough level 10–20 mg/l).

The aim of our study was to evaluate the rates of therapeutic range vancomycin trough levels (10–20 mg/l) within the routine monitoring of a major third level hospital and their association with nephrotoxicity.

Therefore, data of patients who received vancomycin during the period from 1 January 2011 to 31 December 2012 at Rostock University Medical Center Hospital was retrospectively evaluated. Patients were included if they were ≥18 years old, had ≥3 vancomycin trough levels measured during the therapy and corresponding serum creatinine levels within 48 hours of vancomycin trough level control. Nephrotoxicity following the initiation of vancomycin therapy was defined as an increase in serum creatinine level of 50% at two consecutive measurements. Particularly, vancomycin trough levels and serum creatinine levels after the third and seventh day of therapy were examined.

During the study period 259 patients (154 male, 105 female, 21–92 years) with 280 vancomycin therapy cycles were evaluated.

After the third day of therapy 8.21% of vancomycin trough levels were <5 mg/l, 32.86% 5–10 mg/l, 30.36% >10–15 mg/l, 15.36% >15–20 mg/l and 13.21% >20 mg/l, respectively. After the seventh day of therapy 7.69% of vancomycin trough levels were

<5 mg/l, 32.69% 5–10 mg/l, 40.38% >10–15 mg/l, 15.38% >15–20 mg/l and 3.85% >20 mg/l, respectively. Over the course of vancomycin therapy there were 9 patients (3.47%) with evidence of nephrotoxicity identified as an increase in serum creatinine level of 50%.

Overall, underexposure of vancomycin was more evident in routine clinical practice than overexposure. Implementation of new treatment guidelines and routines takes some time, since one third of trough levels was kept targeted in the traditional target range (5–10 mg/l). However, over the course of therapy an increase of sufficient vancomycin trough levels into the therapeutic range of 10–20 mg/l from 45.72% to 55.76% was observed. This is especially achieved by the considerable reduction of nephrotoxic trough values above

20 mg/l, which is accompanied by a low rate of increasing serum creatinine levels.

In conclusion our results confirm the clinical benefit of TDM during a vancomycin based anti-infective therapy.