Accuracy of vancomycin trough levels: An experience at a large university based hospital

To analyze the results from the clinical monitoring of serum vancomycin levels among our patients receiving this drug, we have done a retrospective study of data from routine monitoring of serum vancomycin concentrations. The study population includes adult patients who received vancomycin for more than 3 days and had a trough vancomycin serum concentration documented. We obtained 30 vancomycin concentrations from our patients. With a mean trough concentrations was 12.3 micrograms/mL. Only 32% of the patients were on the normal ranges, 27% were above the range and 40% under the lower limit. Also we found that only in 25% of the time the initial dosage of the vancomycin was calculated correctly based on the patient's actual body weight and only in < 50% of the time the maintenance dose of vancomycin was calculated based on the creatinine clearance. This might be explained by the type of the population sampled, reflecting a selection bias by detecting levels only among patients with an increased risk for toxicity. Finally, we stress the importance of accurately documenting dose, timing, and renal function in the records of all patients subjected to serum vancomycin determinations.