Therapeutic Drug Monitoring of Vancomycin: The Relationship Between Trough Plasma Concentration and Creatinine Clearance

Background: In this study which was conducted in Besat hospital (Hamadan, Iran), the therapeutic drug monitoring (TDM) of vancomycin (VAN) was carried out based on the quantification of VAN trough in intensive care unit (ICU) patients. Methods: The study population was selected from ICU patients treated by intravenous VAN. To determine VAN trough, blood samples were taken from patients before the fourth dose. Then, trough concentrations were determined by newly developed high-performance liquid chromatography (HPLC) and compared with the conventional method of immunoassay. Twenty patients were included based on the aim of the study. Results: The mean value of the trough for the studied patients was 26.31±18.05 μg/mL. For 16 (80%) patients, trough levels were found to be less than 10 μg/mL. For 12 (60%) patients, creatinine clearance was less than 90 mL/min and more than 120 mL/min. The mean value of creatinine clearance for the studied patients was 95.49± 25.74 mL/min. Based on the results, there was a significant relationship between VAN trough concentration and creatinine clearance (P=0.045). Conclusion: In general, the HPLC method is more sensitive than immunoassay for the determination of VAN in plasma samples. However, VAN dosing based on creatinine clearance is not enough for achieving the goal trough level but measuring the creatinine clearance and trough concentration are considered as vital aspects for the TDM of VAN.