Pharmacokinetic disposition of cefazolin in serum and tissue during canine total hip replacement

Intraoperative cefazolin concentrations were measured in serum, joint capsule, cancellous bone of the acetabulum, and proximal cancellous bone of the femur in 15 dogs undergoing total hip replacement. Cefazolin (22 mg/kg intravenously [IV]) was administered every hour for three doses. The mean peak serum concentrations (+/- SEM) were 387.79 +/- 27.56 micrograms/mL, 521.71 +/- 28.00 micrograms/mL, and 542.20 +/- 30.91 micrograms/mL, respectively. Mean serum concentrations just before administration of doses 2 and 3 were 51.77 +/- 2.39 micrograms/mL, and 64.84 +/- 3.46 micrograms/mL, respectively. The mean cefazolin concentrations in the joint capsule, cancellous bone of the acetabulum, and cancellous bone of the femur were 34.71 +/- 2.50 micrograms/g, 28.70 +/- 7.40 micrograms/g, and 36.20 +/- 3.80 micrograms/g, respectively. The minimum inhibitory concentration of cefazolin for 90% of the common contaminants (MIC90) in this clinic is less than or equal to 2 micrograms/mL or per gram of tissue. Serum concentrations never fell below 15 times the MIC90 (lowest trough, 35.93 micrograms/mL), and the lowest tissue concentration (6.57 micrograms/mL in cancellous bone from the acetabulum) was still more than 3 times the MIC90. The mean tissue concentration was 15 times the MIC90.