Background Initial intravenous dosing with vancomycin should be based on actual body weight (ABW) and subsequent dose titration based on renal function and serum trough concentrations. The manufacturer´s labelling recommends 500 mg/6 h or 1000 mg/12 h (the most commonly used dose).

Purpose To analyse the frequency of vancomycin overdose when a standard dose of 1000 mg/12 h is used, and its association with age, gender and creatinine clearance (CrCl).

Material and methods Retrospective observational study between January 2014 and September 2015. All patients treated with at least four doses of vancomycin were included. Age, gender, ClCr and trough level of vancomycin, collected before the fourth dose, were obtained. Patients were classified according to age (65 years), gender and ClCr (50 mL/min). Thereafter, data were related to trough levels of vancomycin (>20 μg/mL was considered an overdose). Bivariate analysis was carried out to identify variables associated with overdosing with χ² or Fisher exact test.

Results 75 patients were included, 46 male (61.3%), mean age 68.7 ± 13.8 years. Patients overdosaged were 25 (33.3%). Patients were classified as shown in table 1.

No association between gender and overdose was found (p = 0.241). Statistical analysis suggested a significant relationship between baseline CrCl <50 mL/min and overdose (OR=14.5; 95% CI 3.5 to 59.1; p < 0.01) and age >65 years and overdose (OR=4.1; 95% CI 1.1 to 15.7; p = 0.029).

Conclusion A prefixed dose of vancomycin of 1000 mg/12 h, particularly in patients >65 years old and in renal impairment could lead to toxic levels.

Although data regarding the optimal initial dose of vancomycin in the elderly are scarce, our results are consistent with those reported by Guay et al .¹

The initial vancomycin dose should be individualised according to ABW, age and renal function, and subsequent dosing should be adjusted based on serum trough vancomycin concentrations.

References and/or Acknowledgements

1. Guay DRP, Vance-Bryan K, Gilliland S, et al. Comparison of vancomycin pharmacokinetics in hospitalized elderly and young patients using a Bayesian forecaster. J Clin Pharma 1993;33:918–22

References and/or AcknowledgementsNo conflict of interest.