Association of vancomycin serum concentrations with outcomes in patients with gram-positive bacteremia

We attempted to determine if an association exists between vancomycin serum concentrations resulting from traditional dosing regimens, and efficacy and toxicity outcomes. We reviewed the medical charts of 273 consecutive patients prescribed 273 courses of vancomycin therapy for documented, gram-positive bacteremia. Of the 273 courses of therapy, 45 and 31 patients met all criteria and were evaluated for toxicity and efficacy, respectively. The duration of fever and abnormal white blood cell counts, length of hospital stay, overall mortality, serum creatinine, and serum vancomycin concentrations were evaluated retrospectively. No association between initial peak or trough levels with mortality was noted. However, patients were more likely to become afebrile within 72 hours if peak and trough concentrations were 20 micrograms/ml or greater and 10 micrograms/ml or greater, respectively (p < 0.01). Patients were also more likely to have their white blood cell count return to normal within 72 hours if trough concentrations were 10 micrograms/ml or above (p < 0.01). No statistically significant correlation between nephrotoxicity and initial serum creatinine, days of hospital stay, or days of vancomycin therapy were found. Serum concentrations of vancomycin, assessed before the development of nephrotoxicity, were significantly higher in patients who became nephrotoxic. Mean (SD) trough concentrations were 23.2 (2.5) micrograms/ml and 10.2 (3.8) micrograms/ml in nephrotoxic and nonnephrotoxic patients, respectively. Our results suggest that the commonly accepted therapeutic range for vancomycin trough concentrations (< 10 micrograms/ml) may be too restrictive in patients receiving vancomycin therapy alone.