Evaluation of trough-based vancomycin therapy in achieving targeted area under the curve in haemodialysis cases.

Background & Objectives: Recently published IDSA guidelines on vancomycin dosing no longer advocates the use of trough concentrations as surrogate markers for clinical efficacy.  Protocols developed prior to revised targets may not reflect to the true efficacy marker for vancomycin that is AUC/MIC 400-600. This study aimed to evaluate the local vancomycin dosing protocol in achieving the target trough concentration and extrapolated AUC/MIC of 400-600 in patients with haemodialysis. Methods: A retrospective analysis of therapeutic drug monitoring forms and individual medical records of haemodialysis patients was conducted. Vancomycin AUC of each individual was extrapolated via the use of a pharmacokinetic modelling software, PrecisePK®. Chi-square test of independence was used to determine the association of factors affecting AUC/MIC. A p value of 0.05 was considered statistically significant. Results: A total number of 80 haemodialysis-dependent cases who were on vancomycin were recruited. More than 62% of haemodialysis patients showed AUC/MIC > 800. AUC/MIC was heavily influenced by minimum inhibitory concentration of the infecting microorganism. Interpretation & Conclusions: Exclusive trough-guided dosing may not translate well in achieving clinical efficacy of vancomycin in haemodialysis patients. Other contributing factors, especially MIC should be factored, as small MIC values account for greater reciprocal AUC/MIC values that increase the risk of loss of residual kidney function; a factor which is associated with overall mortality of HD patients.