Vancomycin therapeutic drug monitoring in paediatrics

Vancomycin guidelines for therapeutic drug monitoring (TDM) aim to maximise efficacy while minimising toxicity and resistance. Vancomycin is effective against Staphylococcus aureus when it achieves area under the concentration-time curve (AUC)/minimum inhibitory concentration (MIC) > 400. Studies in children have shown that target trough concentrations poorly correlate to AUC/MIC > 400; however, they are used in practice for clinical convenience. This review in paediatric inpatients aims to audit performance against TDM guidelines and consider what changes are needed to optimise vancomycin monitoring.

Vancomycin prescriptions in patients younger than 18 years old were collected over a 15-month period. Primary outcome measures were vancomycin initial dose (mg/kg/day) and the timing and result of first trough concentration (mg/L). Secondary outcome measures were the numbers achieving recommended targets and whether appropriate dose adjustments were made in response to TDM.

A total of 133 courses reached the time when TDM should occur. Average patient age was 6.5 years, and the average initial dose was 52.55 mg/kg/day (range 19.05-86.54 mg/kg). Only 25% of courses (n = 34) had a trough concentration measured at the recommended time. The mean trough concentration was 11.6 mg/L (range < 2.0-39.7). Of 40 patients with a low trough concentration, 50% continued without dose adjustment.

As shown in the literature, there is a poor correlation between the vancomycin dose given and the trough concentration achieved. Given that recommendations for trough concentration monitoring are designed to simplify the process yet are poorly adhered to, a strategic plan to address these issues is needed.