Bone concentrations of antimicrobial agents after parenteral administration

Bone concentrations of seven antimicrobial agents were determined after parenteral administration. Antibiotics were administered in large doses at customary intervals for 12 to 20 h before total hip or knee replacement; anticipated levels of each drug were achieved in the serum. Methicillin, carbenicillin, and clindamycin were detected in bone with greatest frequency. Cefazolin and gentamicin were each detected in bone specimens from only one of four patients. Neither penicillin G nor cephalothin was present in bone in sufficient quantity to be measurable. These data suggest that a number of factors, in addition to serum concentration, affect concentration of antimicrobial agents in bone. The clinical significance of the relationship between bone concentrations of antibiotics and therapeutic outcome is not certain.