Therapeutic Drug Monitoring of Vancomycin

Vancomycin, a glycopeptide antibiotic, was developed and released in the 1950's for the treatment of aerobic gram-positive infections and has been widely used mainly in the treatment of methicillin-resistant Staphylococcus aureus infections. Early reports regarding the possibility of nephrotoxicity and ototoxicity led to concern about the use of vancomycin and the need to monitor serum concentrations. In Mexico, the National Institute of Cardiology measures serum level of some drugs, such as vancomycin on a routine basis. Nevertheless, although a large number of measurements are made, the quantification of drug in serum is only used by physicians as a empiric parameter for dose adjustment. The aim of this work was to know whether dosing was appropriate taking the therapeutic interval as a commonly accepted baseline and to propose viable alternatives in the case dosing was inadequate. Peak and through vancomycin levels were analyzed retrospectively (n=295), in patients from 18 to 65 yr old with diagnosis of sepsis. The relationship between administered dose and measured blood levels was established. The equation that characterizes the study population was obtained based on a single compartment model considering the proportional relationship between vancomycin and creatinine clearance. The analysis shows that only 44% of Ctrough and 47% of Cpeak values represented therapeutic levels, with the remainder either toxic or ineffective.