Distribution of gentamicin from a Gentacoll sponge measured by in vivo microdialysis

Microdialysis has produced valuable information concerning the distribution of antibiotics in peripheral tissue. The aim of this study was to measure the local distribution of gentamicin in cancellous bone tissue after the application of a Gentacoll sponge. Two microdialysis catheters were inserted into the cancellous bone of 9 pigs. After calibration of the microdialysis, a Gentacoll sponge was implanted, either dry or wet, into the bone marrow of the tibia. Serum and microdialysates were obtained over a period of 6 h. Data presented are median (range). A rank sum test was performed for statistical analysis. The peak concentration was 120 mg/l (33-585) (wet group) and 178 mg/l (60-1294) (dry group) (p=0.31). The AUC6 of the catheters placed 1 cm away from the implant was 24,431 mg*min/l (5155-152,855) and the AUC6 of the catheter placed 2 cm away from the implant was 13,759 mg*min/l (6351-74,573) (p=0.25). The study showed that peak concentrations and AUC6 did not differ between the wet- and dry-application group; neither did the distance from the sponge to the catheter have a significant impact on the distribution of gentamicin. It seems that microdialysis is capable to measure concentrations of locally applied antibiotics.