How vancomycin is used in Australasia--a survey.
BACKGROUND
Vancomycin serum concentrations have been monitored over the last 30 years in an attempt to avoid dose-dependent toxicity and enhance efficacy. Current literature recommendations for peak and trough concentrations are usually in the range of 20-40 mg/L and 5-10 mg/L, respectively. Literature recommendations regarding the time at which peak concentrations are measured are highly variable, ranging from immediately after the end of the infusion to three hours post-dose.


OBJECTIVE
To identify how vancomycin dosing is being monitored and assess variability in the current practice.


METHODS
A survey of microbiology departments and infectious disease physicians in major Australasian hospitals was undertaken. The variability in the current practice was assessed by fitting mean recommendations to a two compartment Bayesian model.


RESULTS
Of the 83 (70%) who replied 71 (86%) monitored vancomycin concentrations. Fifty-four percent targeted peak concentrations within the range of 20-40 mg/L, and 73% targeted trough concentrations < or = 10 mg/L. The time of sampling of peak concentrations varied considerably ranging from immediately (12%) to 120 minutes (12%) post-infusion (median 30 minutes [40%]). The concentration-time curves resulting from three sets of mean recommendations ('peaks' drawn at: 0, 30 and 120 minutes aiming for a concentration of 35 mg/L with a trough concentration of 10 mg/L) were modelled using a two compartment Bayesian programme. The predicted true peak (maximum) concentrations ranged from 30 to 86 mg/L, despite aiming for identical target concentrations, indicating marked variation in the actual dosing practice.


CONCLUSIONS
There is thus considerable variation in the practice of vancomycin therapeutic monitoring which has a major effect on dosing. The main contributing factor is the variable timing of sampling peak concentrations.
Duffull
S B
SB
Clinical Pharamcology Department, Christchurch Hospital, NZ.
Chambers
S T
ST
Begg
E J
EJ
D001315:Australia; D003625:Data Collection; D016903:Drug Monitoring / Q000706:statistics & numerical data; D006801:Humans; D014640:Vancomycin / Q000008:administration & dosage* / Q000097:blood
D014640:Vancomycin