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

Area of Science:

• Pharmacokinetics
• Biomaterials Science
• Orthopedic Research

Background:

• Gentamicin is a crucial antibiotic for treating bone infections.
• Accurate measurement of gentamicin in bone tissue is vital for optimizing treatment efficacy and minimizing toxicity.
• Current methods for assessing bone antibiotic levels can be invasive or provide limited dynamic data.

Purpose of the Study:

• To evaluate the suitability of microdialysis for dynamic and quantitative measurement of gentamicin concentrations in cortical bone.
• To compare microdialysis-derived gentamicin levels with those obtained from bone specimens.
• To assess the reproducibility of the microdialysis technique in vivo.

Main Methods:

• Microdialysis catheters were inserted into the tibial diaphyses of 10 healthy pigs.
• Intravenous gentamicin (160 mg) was administered as a bolus.
• Serum, dialysate, and bone specimen samples were collected over 6 hours for gentamicin concentration analysis.
• Reproducibility was assessed using paired catheter measurements and AUC ratios.

Main Results:

• Peak gentamicin concentrations in microdialysis probes (3 mg/L, 2.9 mg/L) and bone specimens (2.6 mg/L) were comparable (p = 0.3).
• Areas under the curve (AUC6h) for microdialysis and bone specimens showed similar trends (704, 661, and 569 mg/min/L; p = 0.07).
• The reproducibility ratio for microdialysate AUC(6h) between two catheters was 1.12, indicating good consistency.

Conclusions:

• Microdialysis is a suitable method for dynamic and quantitative assessment of gentamicin in cortical bone.
• The technique provides reliable data comparable to traditional bone specimen analysis.
• This method holds promise for pharmacokinetic studies and therapeutic drug monitoring in bone infections.