Impact of Vancomycin Therapeutic Drug Monitoring on Patient Care

Abstract

To document differences in the outcome of vancomycin therapy in patients managed through a therapeutic drug monitoring (TDM) service and patients managed empirically, without the participation of a TDM service. Prospective, cohort study. An 1100-bed, tertiary-care, teaching hospital. Those who received vancomycin for more than four days, were at least 18 years old, had an estimated creatinine clearance of more than 0.33 mL/s (20 mL/min), were not neutropenic at the start of vancomycin therapy, and were not treated in a critical care unit were enrolled in the study. A total of 116 patients (61 TDM; 55 non-TDM) were monitored prospectively from June 1990 through March 1991. Patients in the TDM group had vancomycin drug therapy monitored daily by a pharmacist and vancomycin dosages adjusted following a pharmacokinetic analysis of vancomycin serum concentrations. For patients in the non-TDM group, the pharmacist only completed a data collection form. The patients and physicians were unaware of the monitoring. Duration of therapy, total vancomycin dosage, infection site, concomitant antibiotics, body temperature, and white blood cell counts were compared between the two groups. Length of stay data were also compared. Nephrotoxicity was evaluated by comparing serum creatinine concentration and estimated creatinine clearance. TDM of vancomycin appeared to reduce the incidence of vancomycin-related renal insufficiency (TDM 7 percent; non-TDM 24 percent). Patients managed through the TDM service received an average of 5 g less of vancomycin than did the patients in the non-TDM group. The duration of vancomycin therapy was an average of 2 days less for patients in the TDM group. Mean length of stay was 38.0 days for the TDM group and 44.5 days for the non-TDM group. Other measures of efficacy, infection site, and concomitant antibiotics were the same for both groups. TDM of vancomycin was associated with fewer cases of vancomycin-related renal insufficiency. Vancomycin efficacy was not compromised by TDM. Provision of TDM for vancomycin therapy aided in patient management.