A new approach to antibiotic therapy in colon surgery based on bioassay tissue concentrations.

The authors investigated the kinetics, in serum and tissues, of clindamycin, metronidazole, cefoxitin and moxalactam given during colon surgery in the dog. Colon, rectus muscle and subcutaneous fat samples were taken at times of maximal contamination during the initial operation and at a second operation, 9 days after the first, when septic complications were most likely to occur in the healing tissues. Bioassay was used to measure the amount of active antibiotics in serum and tissues. Clindamycin achieved therapeutic levels in all tissues except those of the fresh wound, thus making it a better therapeutic than prophylactic agent. Metronidazole achieved therapeutic levels in both fresh and healing tissues. Cefoxitin and moxalactam did not achieve adequate levels in either fresh or healing tissues.