In situ gentamicin concentrations in cortical bone: an experimental study using microdialysis in bone.

We used microdialysis to study gentamicin in cortical bone and compared these results to values obtained in bone specimens. 10 healthy pigs were given an intravenous bolus of 160 mg of gentamicin. We measured reproducibility by inserting two microdialysis catheters into the cortex of tibial diaphyses and by taking samples of serum, dialysates and bone specimens during 6 hours and measuring the concentrations of this antibiotic. The peak concentrations in the two microdialysis probes and bone specimens were 3 mg/L, 2.9 mg/L and 2.6 mg/L (Anova, p = 0.3). Similarly, the areas under the curve from 0 to 6 hours (AUC6h) were 704 mg/min/L, 661 mg/min/L and 569 mg/min/L (Anova, p = 0.07). The reproducibility of the measurements of the microdialysates was evaluated with the mean AUC(6h/catheter no.1)/AUC(6h/catheter no. 2) ratio, which was 1.12. It seems that microdialysis is a suitable method for making dynamic and quantitative measurements of gentamicin in bone.