Development and Implementation of New Guidance for Prescribing and Monitoring Vancomycin

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Development and Implementation of New Guidance for Prescribing and Monitoring Vancomycin for Haemodialysis Patients

Helen Thomas1, Robert Bradley1, Gareth Roberts2 and Abdulfattah Alejmi3

1Renal Pharmacist, University Hospital of Wales, Cardiff; 2Consultant Nephrologist, University Hospital of Wales, Cardiff; 3Consultant Nephrologist, Ysybty Gwynedd, Bangor

Introduction

Vancomycin is often used as empirical therapy for central venous catheter (CVC) associated infection. As vancomycin is removed by high-flux haemodialysis (HD), and is a narrow therapeutic index drug, dosing can present a problem. At our unit, regular HD patients requiring vancomycin are dosed on dialysis days only, with pre-dialysis vancomycin levels taken on a weekly basis.

An audit of our previous guidance (target range 5-15mg/L) showed that the mean achieved level was 8.4mg/L. Current evidence shows that higher vancomycin levels (target range 15-20mg/L) should be sought in order to prevent resistance, treatment failure and complications (such as endocarditis). There is also a correlation between the drug’s volume of distribution and the patient’s weight, so it is important to take weight into account for initial dosing in order to achieve therapeutic levels quickly.

Method

New guidance was developed incorporating a weight based loading regime and a new target range of 15 to 20mg/L. An audit was undertaken in 2012 to determine what the mean achieved level was with the new guidance and to identify whether compliance with the protocol had improved.

Results

Forty-four patients were prescribed vancomycin and for those patients 124 levels were taken, on the renal wards and three of the haemodialysis units during the 3 month audit period. Additional analysis on 31 patients showed that 54% did not receive the correct initial weight-based dose.

Vancomycin Levels / 2008 (n=113) / 2012 (n=124)
Mean / 8.4mg/L / 16mg/L
Median / - / 14.9mg/L
In range / 70% (5-15mg/L) / 29% (15-20mg/L)
10-25mg/L (acceptable) / - / 82%
>25mg/L (toxicity risk) / 0% / 7%
>20mg/L / 0% / 20%
>15mg/L / 7% / 50%
<10mg/L (resistance risk) / - / 11%
<5mg/L (subtherapeutic) / 23% / <1%

Table One: Achieved Vancomycin levels before and after implementation of new guidance

Conclusions

In summary, the audit demonstrates that the revised guidance achieves an effective mean pre-dialysis vancomycin level, low frequency of potentially toxic levels (>25mg/L),82% of levels within an acceptable range(10-25mg/L) andnegligible subtherapeutic levels (<5mg/L). Although only 29% of levels were within the target range, this could be improved by better compliance with the weight-based loading element of the guidance, which would also likely increase our mean vancomycin level. This highlights the importance of the pharmacist working closely with the renal multidisciplinary team to ensure that vancomycin is prescribed and monitored correctly for each patient.