Reevaluation of ceftazidime dosing recommendations in patients on continuous ambulatory peritoneal dialysis

While intraperitoneal (i.p.) ceftazidime is commonly used to treat continuous ambulatory peritoneal dialysis (CAPD)-related infections, the ability of i.p. regimens to achieve critical pharmacodynamic targets in both blood and dialysate has not been reported. To understand the pharmacodynamic profile of ceftazidime during CAPD, data were obtained from a single-dose pharmacokinetic (PK) i.p. ceftazidime study that included 10 CAPD patients who received i.p. ceftazidime at 15 mg/kg of body weight. The probability of target attainment (concentrations maintained above the MIC for >60% of the dosing interval [60% T > MIC]) was determined for six simulated regimens. A 3-compartment model with each dialysis dwell modeled as a separate differential equation was fit to ceftazidime concentrations using BigNPAG. Embedded with the final PK model, serum and dialysate concentration-time profiles of ceftazidime at 1, 1.5, and 2 g i.p. every 24 h (q24h) to q48h were simulated using ADAPT 5. The mean population pharmacokinetic parameters were as follows: apparent volume of the central compartment (Vc), 7.57 liter; apparent volume of the peritoneal cavity (Vpd), 2.44 liter; clearance from the central compartment (CL), 0.379 liter/h; intercompartmental transfer rate constants (first order) between the central and peripheral compartments (k12 and k21), 4.66 and 4.88 h(-1), respectively; and intercompartmental transfer rate constants (first order) between the central and peritoneal compartments (k13 and k31), 0.111 and 0.227 h(-1), respectively. In serum, the probability of target attainment for MICs of ≤8 mg/liter exceeded 90% for 1.5 to 2 g i.p. q24h to q48h. However, no tested regimen provided adequate dialysate exposure at MICs of ≥8 mg/liter on day 1 without the use of a 3-g loading dose (post hoc analysis). On day 2, 1.5 to 2 g i.p. q24h or 2 g i.p. q48h provided adequate exposure in the peritoneal cavity. These results should be validated in the presence of infection. Ceftazidime i.p. at 1.5 or 2 g q24h to q48h is recommended for nonperitoneal infections. For peritonitis, a 3-g load with maintenance dosing of 1 to 2 g i.p. q24h or 2 g i.p. q48h is recommended.

Pharmacokinetics of intermittent intraperitoneal ceftazidime

Ceftazidime is currently recommended as an alternative first-line agent in the treatment of peritonitis and for Pseudomonas peritonitis. The pharmacokinetics of intermittent intraperitoneal (i.p.) ceftazidime have been poorly characterized. This study was designed to characterize the pharmacokinetic disposition of a single dose of ceftazidime in anuric and non-anuric CAPD patients, over 48 hours. This was a prospective, open label, pharmacokinetic study. The study was conducted in an independent, outpatient dialysis center. Ten volunteer continuous ambulatory peritoneal dialysis (CAPD) patients with and without residual renal function, no peritonitis or antibiotics in the previous 4 weeks, and on CAPD for at least 2 months were recruited. Patients received a single dose of i.p. ceftazidime (15 mg/kg) in the first daytime exchange over a 6-hour dwell, after an overnight dwell. Serum, urine, and dialysate were collected over a 48-hour period. A high-pressure liquid chromatography (HPLC) assay was used to analyze ceftazidime in these samples. Pharmacokinetic parameters were calculated. Six of the 10 patients were non-anuric with a mean residual renal creatinine clearance of 2.9 +/- 1.6 mL/min. The mean +/- SD bioavailability was 72% +/- 14%, and the volume of distribution was 0.34 +/- 0.08 L/kg. The mean serum elimination half-life of 22 +/- 5 hours. The peritoneal clearance was 5.74 +/- 1.6 mL/min. No difference was detected between anuric and nonanuric patients. Mean plasma and dialysate concentrations at 24 hours were 24 +/- 6 microg/mL and 18 +/- 7 microg/mL, respectively, and were 12.0 +/- 3.6 microg/mL and 7.4 +/- 3.1 microg/mL at 48 hours, respectively. Once-daily i.p. dosing of ceftazidime achieves serum and dialysate levels greater than the MIC of sensitive organisms over 48 hours.