The Disposition of Cefazolin and Tobramycin following Intraperitoneal Administration in Patients on Continuous Ambulatory Peritoneal Dialysis

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Abstract
Two groups of patients with bacterial peritonitis were studied to examine the pharmacokinetics of intraperitoneal tobramycin and cefazolin. In Group I, four patients received tobramycin (5 mg/l) and cefazolin (75 mg/1) in two litres of dialysate for 12 consecutive exchanges. In Group 2, five patients received a loading dose of tobramycin (50 mg/1) and cefazolin (500 mg/l) intraperitoneally in exchange one. In exchanges three through 12, the maintenance schedule was tobramycin (7.5 mg/1) and cefazolin (250 mg/l). Tobramycin was measured by EMIT and cefazolin (in Group 2 only) by HPLC. Serum and dialysate levels were determined at the end of each of 12 exchanges. In Group 1, steady -state tobramycin levels appeared in 48 hours in both serum and dialysate to levels of 2.1 ± 0.2 μg/ml (x ± SEM) and 2.5 ± 0.3 μg/ml respectively. In Group 2, the loading dose schedule provided levels in serum at the end of the first dwell for tobramycin of 4.3 ± 0.64 μg/ml and for cefazolin 54.8 ± 6.7 μg/ml. Steady state levels for tobramycin and cefazolin were 3.7 ± 0.15 μg/ml and 110.9 ± 8 μg/ml respectively. Concomitant dialysate levels for tobramycin were 3.9 ± 0.17 μg/ml and for cefazolin 80.6 ± 26 μg/ml.