Experimental Study Of Antibiotics Penetration Into Normal Rabbit Nucleus Pulposus

Background DataDisc-space infection is a complication of spinal surgery that may be prevented by prophylactic antibiotics. The role of antibiotics in the treatment of secondary & primary disc-space infection is controversial. Several groups of investigators demonstrated quantitative changes in penetration of antibiotics into intervertebral disc. This study assessed the tissue penetration of penicillin & clindamycin into the normal rabbit intervertebral disc after intravenous administration of antibiotic.Materials and MethodsA rabbit model was used to determine the penetration of two commonly used antibiotics (penicillin & clindamycin) into the nucleus pulposus. Fourteen rabbits were distributed into two groups, and then were given a series of 5-halflife course of intravenous injections of antibiotics. Specimens of serum were obtained and prepared at one half-life of antibiotic after injection. Then the rabbits were killed immediately and nucleus pulposus were obtained and prepared. Concentrations of two antibiotics in the serum and in the intervertebral disc tissue were measured with high-pressure liquid chromatography (HPLC).Results and DiscussionClindamycin(positively charged) penetrated the negatively charged nucleus pulposus and were present in greater than 40% of serum levels. Penicillin(negatively charged) had less ability than clindamycin to penetrate into the negatively charged nucleus pulposus and penetrated at less than 1% of serum levels after injection. Despite high blood levels, no penicillin could be detected by high-pressure liquid chromatography(HPLC) in some of the specimens from the nucleus pulposus. Uptake was significantly higher with positivety-charged clindamycin compared with negatively-charged penicillins. Our results support the hypothesis that electrostatic interaction between charged antibiotics and negatively charged glycosaminoglycans in the disc is an important factor in antibiotic penetration, and may explain their differential uptake.ConclusionsOur data suggest that penetration and distribution of antibiotics into avascular intervertebral disc is significantly influenced by the charge of antibiotics. Because rabbit nucleus pulposus is similar anatomically to that of humans, these results may have implications regarding the choice of antibiotic administration. Clindamycin can be used in conjunction with other antibiotics as a prophylactic agent.