Initiation of vancomycin therapy and the first therapeutic drug monitoring

There have been a limited number of studies in Latvia that were focused on vancomycin therapeutic drug monitoring (TDM), especially during the initiation phase of the therapy. The aim of this study was to investigate details of vancomycin therapy in its initiation phase and to analyse the results of the first therapeutic drug monitoring within a multidisciplinary hospital in Latvia. A retrospective observational study was performed in a multidisciplinary hospital in Latvia. Adult patients hospitalised in an intensive care unit and undergoing vancomycin therapy with at least one concentration measurement were included in this study. Data about patients included demographic and clinical data, renal function prior to initiation of vancomycin therapy, data about vancomycin therapy, data about the first TDM, and details about the first measurement of vancomycin concentration according to determined reference range — subtherapeutic, therapeutic and supratherapeutic levels. A total of 60 intensive care unit patients who received vancomycin with at least one concentration measurement were included in this study. Fifty-eight patients received vancomycin as intermittent intravenous infusion. The first measurement of concentration was taken before the 3^rd–4^th vancomycin dose in 38.3% cases, and in 33.3% cases — before the 2^nd dose. Sampling to determine the concentration within 30 minutes before vancomycin administration was performed in zero cases. In 35% cases, sampling was done within 2–5 hours before vancomycin administration and in 23.3% — immediately after or within a few hours after vancomycin infusion. Twelve (20%) patients had a concentration in the subtherapeutic level, and 14 (23.3%) patients had concentrations above the therapeutic level. In 42.8% of patients who had concentrations in supratherapeutic level, sampling had been performed immediately after or within several hours after vancomycin administration. The first concentration measurement was performed more than one hour before an infusion in all cases. Data on concentrations and timing were not adequate to perform appropriate therapy modification. Interpretation of dosing regime and concentration results were not adequate, and therefore correct modification of vancomycin therapy was often not possible. Routines of correct dosing regime and the 1^st TDM during the initiation phase of vancomycin therapy can be improved.