Gentamicin penetration into normal rabbit nucleus pulposus

Abstract

Study design: Radioactively labeled gentamicin was administered to 24 rabbits to assess the concentration of antibiotic in the nucleus pulposus.

Objectives: The purpose of the study was to investigate the pharmacokinetics of gentamicin penetration into normal rabbit nucleus pulposus.

Summary of background data: Disc space infection is a complication of spinal surgery that can be prevented by prophylactic antibiotics. Gentamicin can be used in conjunction with other antibiotics as a prophylactic agent. One previous study demonstrated that a similar antibiotic, tobramycin, penetrates the disc, but no data have been reported on the pharmacokinetics of disc penetration.

Methods: Twenty-four rabbits were given an intravenous injection of gentamicin labeled with iodine 125. Four rabbits were killed at hourly intervals 1 to 6 hours after injection. Specimens of nucleus pulposus, blood, whole liver, and saline-perfused liver were obtained and prepared. The radioactivity in the specimens was measured.

Results: The gentamicin concentration in the nucleus pulposus peaked at 2 hours and remained at this level for the duration of the experiment. Twenty percent of the gentamicin recovered from the nucleus pulposus was tissue bound.

Conclusions: Gentamicin concentration in the rabbit nucleus pulposus does not peak until 2 hours after an intravenous bolus of drug. If gentamicin penetrates human nucleus pulposus in a similar fashion, this study could have implications for the timing of administration of this agent for prophylaxis.