Intermittent intraperitoneal ceftazidime dosing in end-stage renal disease

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 intraperitoneal cefazolin and ceftazidime coadministered to CAPD patients

PURPOSE

Guidelines for empiric treatment of PD-related peritonitis published in 2000 recommend concurrent intraperitoneal (IP) cefazolin and ceftazidime. The pharmacokinetics (PK) of these agents combined have not been studied. This study was designed to determine the PK of combined IP cefazolin and ceftazidime in CAPD patients.

DESIGN

Prospective PK study in seven non-infected CAPD patients.

PROCEDURES

Patients had a peritoneal equilibration test (PET), then received one IP dose of cefazolin and ceftazidime (15 mg/kg each) co-administered over a 4-hour dwell, then performed three CAPD exchanges over the next 16 hours. Serum and dialysate samples collected over the 20-hour study period were assayed for drug concentrations by HPLC.

OUTCOME MEASURES

PK parameters.

STATISTICAL METHODS

Correlations were tested between PET and PK parameters using the Pearson-product correlation coefficient.

MAIN FINDINGS

Serum cefazolin and ceftazidime levels exceeded the minimum inhibitory concentrations for susceptible organisms (8 mg/L) throughout the 20 hour study period. Mean cefazolin and ceftazidime PK parameters included: bioavailability, 71% and 63%; elimination rate constant, 0.031 and 0.045 h -1 ; total clearance, 5.8 and 16.0 ml/min; peritoneal clearance, 1.6 and 3.9 ml/min; renal clearance, 2.3 and 3.9 ml/min, respectively. Predictive equations suggest that 1000 mg IP of cefazolin and of ceftazidime every 24 hours would produce average steady-state trough serum cefazolin and ceftazidime concentrations of 70 +/- 52 mg/L and 17 +/- 7 mg/L, respectively. There was no correlation between PET and PK parameters.

CONCLUSIONS

Co-administration did not adversely affect the PK of either agent. IP cefazolin and ceftazidime (15 mg/kg) produced adequate serum and dialysate concentrations in CAPD patients for 20 hours. PK predictions suggest that most patients would achieve adequate cefazolin and ceftazidime concentrations with 1000 mg IP once-daily. Anuric patients and those with significant residual renal function may require a more individualized approach.

Infections in patients undergoing peritoneal dialysis

Considering experience acquired in the past years, it seems as though physicians have reached a plateau in the frequency of peritonitis. A peritonitis rate of 1 every 2 patient years may be acceptable. Further reduction of this peritonitis rate will require inordinately large efforts on all fronts. One will have to consider what are the acceptable costs and risks of peritonitis in patients on peritoneal dialysis. New developments in catheter technology, improved connections, better understanding of patient selection and training programs, improved diagnostic and therapeutic methods in the management of peritonitis, and understanding of the infectious and immune processes are eagerly awaited developments.