Effects of renal failure and dialysis on cefazolin pharmacokinetics

Drugs and Peritoneal Dialysis

This paper is a review of the literature describing drug disposition in patients with end-stage renal disease (ESRD) during either intermittent peritoneal dialysis (IPD) or continuous ambulatory peritoneal dialysis (CAPD). The removal of drugs by peritoneal dialysis and drug absorption after intraperitoneal administration are examined. Detailed pharmacokinetic data extracted from the literature are presented in tabular form and are accompanied by specific dosage recommendations for dialyzed patients. Accepted literature values for parameters reflecting the effects of ESRD alone are also included. The construction of a rational dosage regimen with emphasis on the use of the aminoglycosides and the cephalosporins is described.

Removal of doripenem during hemodialysis and the optimum dosing regimen for patients undergoing hemodialysis

The removal of doripenem by hemodialysis was studied in six hemodialysis patients. Following an intravenous drip infusion of 0.5 g of doripenem, plasma concentrations of the drug were measured. The decrease in drug concentrations in plasma was observed during various periods of non-hemodialysis, and hemodialysis accelerated the elimination of doripenem. For example, the calculated mean half-life during hemodialysis was significantly shorter than that during non-hemodialysis periods (P = 0.002). The calculated pharmacokinetic parameters indicated that the mean rate of decrease in plasma concentration due to hemodialysis alone was 56.12 ± 8.11%. Upon obtaining these results and several pharmacokinetic parameters, we attempted to optimize the dosing regimen of doripenem for hemodialysis patients. We recommend the use of 0.25 g of doripenem once a day in patients infected with viable bacteria, and in patients who are infected with Pseudomonas aeruginosa, 0.5 g twice a day on the first day of administration, followed by 0.5 g once a day.

Safety and Efficacy of Cefazolin Sodium in the Management of Bacterial Infection and in Surgical Prophylaxis

Cefazolin sodium is a first-generation cephalosporin antibiotic and has been used worldwide since the early 1970s. It is used for the treatment of bacterial infections in various organs, such as the respiratory tract, skin and skin structure, genital tract, urinary tract, biliary tract, and bone and joint infections. It has also been used for septicemia due to susceptible gram-positive cocci (except Enterococcus), some gram-negative bacilli including E. coli, Proteus, and Klebsiella may be susceptible, and for perioperative prophylaxis. After the introduction of penicillins and other cephalosporins, occasional outbreaks of methicillin-resistant Staphylococcus aureus were noted. As a result, vancomycin use was increased; however, very recently and most alarmingly, vancomycin-resistant strains have been described. In this setting, to avoid the risk of the development of vancomycin-resistant strains further, vancomycin use should be curtailed. In consideration of this historical background, the appropriate use of antibiotics, such as dosage, dosage intervals, and the duration of administration is required not only for the protection of patients’ health but also for the prevention of the development of drug resistance. Cefazolin has been used in clinical practice for about 40 years, and a large body of evidence has been accumulated, and its efficacy and safety are well established compared with other antibiotics. Therefore, cefazolin has been chosen as a first-line anti-microbial for prophylaxis after various surgical procedures, including cardiovascular surgery, hysterectomy, arthroplasty and so on. Based on these facts, especially for the prophylaxis of surgical site infections, the first-generation cephalosporin, cefazolin, is now being “re-visited”.

Physiological Modeling for Indirect Evaluation of Drug Tissular Pharmacokinetics under Non-Steady-State Conditions: An Example of Antimicrobial Prophylaxis During Liver Surgery

Cefazolin, a time-dependent first-generation cephalosporin with non-linear binding to albumin, is widely recommended for antimicrobial prophylaxis during liver surgery to decrease the incidence of postoperative wound infections. The recommended protocol (2 g IV at anesthesia induction followed by 1 g 4 h later) is expected to maintain the free cefazolin concentration in exposed intratissular fluids above its minimal inhibitory concentration (MIC) for potentially encountered microorganisms, from skin incision to skin closure. Since this dosing protocol fails to take into account either of patients status (total body weight and renal function) or of surgical and anesthetic consequences (variations of cardiac output and regional blood flows, progressive decrease of plasma albumin concentration) on cefazolin tissular pharmacokinetics, a physiological modeling study was conducted to investigate protocol suitability for liver surgery in six populations: obese (body mass index >34), renal insufficiency (GFR = 10, 30 or 50 ml min(-1)) and high intraoperative blood loss (three times that usually observed during this surgery) and none of these features referred to as controls. A previously validated physiologically based pharmacokinetic (PB-PK) model for cefazolin in humans was used and then further adapted to simulate obese or renal insufficiency patients as well as the consequences of general anesthesia and liver surgery on cefazolin pharmacokinetics. Clinical data required for simulation (intraoperative kinetics of percent expired isoflurane and plasma albumin concentration, mean intraoperative blood loss) were obtained from 10 patients who underwent right hepatectomy in our institution. Using a fixed MIC of 2 microg ml(-1) against potentially encountered bacteria, it was concluded that the recommended dosing schedule was suitable in all tested populations, including obese patients, although prolongation of the interval between injections appeared advisable for renal insufficiency patients. Furthermore, when a MIC of 3 microg ml(-1) was considered, the recommended cefazolin-dosing regimen failed to maintain sufficient free cefazolin concentrations in the interstitial fluids during surgery in all tested populations except renal insufficiency patients (GFR < 50 ml min(-1)).

Cefazolin dialytic clearance by high-efficiency and high-flux hemodialyzers

Cefazolin dialytic clearance has not been determined in patients undergoing hemodialysis with high-efficiency or high-flux dialyzers. The objective of this study is to determine the pharmacokinetics and dialytic clearance of cefazolin and develop dosing strategies in these patients. Twenty-five uninfected subjects undergoing chronic thrice-weekly hemodialysis were administered a single dose of intravenous cefazolin (15 mg/kg) after their standard hemodialysis session. Fifteen subjects underwent hemodialysis with high-efficiency hemodialyzers, and 10 subjects underwent hemodialysis with high-flux hemodialyzers. Blood and urine samples were collected serially over the interdialytic period, during the next intradialytic period, and immediately after the next hemodialysis session. Serum and urine concentrations of cefazolin were determined by high-performance liquid chromatography. Differential equations describing a two-compartment model were fit to the cefazolin serum concentration-time data over the study period, and pharmacokinetic parameters were determined. Mean dialytic clearance values for cefazolin were significantly greater in the high-flux group compared with the high-efficiency group (30.9 +/- 6.52 versus 18.0 +/- 6.26 mL/min, respectively; P: < 0.05). Cefazolin reduction ratios were significantly greater (0.62 +/- 0.08 versus 0.50 +/- 0.07; P: < 0.005) in the high-flux group compared with the high-efficiency group and correlated well with equilibrated urea reduction. The pharmacokinetic model developed from patient data was used to simulate cefazolin serum concentration data for high-efficiency and high-flux dialyzers. Cefazolin doses of 15 or 20 mg/kg after each hemodialysis session maintained adequate serum concentrations throughout a 2- or 3-day interdialytic period regardless of hemodialyzer type.

Pharmacokinetics of once daily intraperitoneal cefazolin in continuous ambulatory peritoneal dialysis patients

This study determined the pharmacokinetic characteristics of once daily intraperitoneal (IP) cefazolin in continuous ambulatory peritoneal dialysis (CAPD) patients. Each of the 10 volunteer CAPD patients without active peritonitis received a single IP dose of 1 g of cefazolin sodium for a 6-h dwell. All patients underwent a fixed CAPD regimen comprising a first 6-h dwell followed by two 3-h dwells and a final 12-h overnight dwell. Blood and dialysate samples were collected at 0, 0.5, 1, 2, 3, 6 (end of first dwell), and 24 h after the administration of IP cefazolin. Any urine produced was collected over the 24-h study period. A validated HPLC method was used to analyze cefazolin in plasma, dialysate, and urine. The bioavailability was found to be 77.9 +/- 3.1%, volume of distribution 0.20 +/- 0.05 L/kg, and plasma half-life 39.9 +/- 25.4 h. Mean total, renal, and peritoneal clearances were 4.5 +/- 2.3, 1. 4 +/- 1.1, and 3.5 +/- 1.8 ml/min, respectively. Mean plasma and dialysate concentrations at 24 h were 42.8 +/- 14.3 and 31.8 +/- 11. 7 mcg/ml, respectively, well above the minimum inhibitory concentrations (MIC) of susceptible organisms. A once daily IP cefazolin dose of 500 mg/L gave desirable pharmacokinetic attributes for use as a suitable alternative to vancomycin for empiric treatment of CAPD-associated peritonitis.

Clinical pharmacokinetics of antibiotics in patients with impaired renal function

Many antibiotics are eliminated renally and dosage adjustments are commonly made in patients with renal insufficiency. This is a critical review of antibiotic pharmacokinetics in patients with various degrees of renal function. Detailed information regarding pharmacokinetic alterations with specific antibiotics or antibiotic classes has been compiled and tabulated. From pharmacokinetic evidence, recommendations for dosage adjustments of antibiotics are supplied. The criteria used for assigning rating levels to specific pharmacokinetic articles as well as the grading system for dosage adjustments are outlined. In addition, a basic review of pharmacokinetic alterations in renal failure and factors affecting the removal of drugs by haemodialysis is included.

Drug therapy in patients undergoing peritoneal dialysis. Clinical pharmacokinetic considerations

Peritoneal dialysis has become an accepted treatment modality for end-stage renal disease. The introduction of continuous ambulatory peritoneal dialysis (CAPD) has further popularised this technique. The need for adjustment of drug dosage in patients with endstage renal disease and the need for supplemental dosages following haemodialysis are well recognised. Little documentation exists concerning the need for supplemental drug dosage in patients on peritoneal dialysis. Knowledge of the influence of peritoneal dialysis on the elimination of specific drugs is essential to the rational design of dosage regimens in patients undergoing this dialysis technique. This review addresses the clinical pharmacokinetic aspects of drug therapy in patients undergoing peritoneal dialysis and considers: the efficiency of the peritoneal membrane as a dialysing membrane; the effects of peritoneal dialysis on the pharmacokinetics of drugs; the pharmacokinetic models and estimation methods for peritoneal dialysis clearance and the effects of peritoneal dialysis on drug elimination; the influence of the pharmacokinetic parameters of drugs on drug dialysability; and the application of pharmacokinetic principles to the adjustment of drug dosage regimens in peritoneal dialysis patients. Data on drugs which have been studied in peritoneal dialysis are tabulated with inclusion of pharmacokinetic and dialysability information.

The pharmacokinetics of antibiotics used to treat peritoneal dialysis-associated peritonitis

Antibiotics continue to be used frequently to treat CAPD-associated peritonitis. Selection of appropriate antibiotic doses and routes of administration has been based largely upon clinical experience. Early pharmacokinetic studies utilized patients being treated with IPD. The relevance of these studies to CAPD remains unknown. Little information exists on the effects of peritonitis on peritoneal drug transport. Until the effects of peritonitis during CAPD are better understood, pharmacokinetic data will be of limited value in designing specific treatment recommendations for this common complication of peritoneal dialysis.

Pharmacology of intraperitoneal cefazolin in patients undergoing peritoneal dialysis

Cefazolin was added to dialysis fluid in nine patients with renal failure undergoing peritoneal dialysis with 2 liters/h per exchange. With 50 mg/liter (three patients), the first measurable mean serum concentration was 3.7 mug/ml (range, 2.4 to 4.9 mug/ml) after three exchanges and was 30.3 mug/ml (range, 13.3 to 44.3 mug/ml) after 24 exchanges. After 18 to 24 more exchanges without cefazolin, the mean serum concentration was 12.3 mug/ml (range, 3.8 to 24.6 mug/ml). The mean concentration in the dialysis outflow was 26.9 mug/ml (range, 2.5 to 58.5 mug/ml). With 150 mg/liter (six patients), the mean serum concentration was 5.2 mug/ml (range, 3.6 to 7.8 mug/ml) after the first exchange and 8.4 (range, 6.1 to 14.0 mug/ml), 15.0 (range, 8.2 to 23.5 mug/ml), and 71.9 (range, 26.2 to 142.1 mug/ml) mug/ml after the second, third, and twenty-fourth exchanges, respectively. After 17 to 24 more exchanges without cefazolin, the mean serum concentration was 38.2 mug/ml (range, 15.4 to 65.7 mug/ml). The mean concentration in the dialysis outflow was 71.4 mug/ml (range, 21.9 to 150.8 mug/ml). After 1 g of cefazolin was given intraperitoneally with no more dialysis, serum concentrations rose by a mean of 62.5 mug/ml (range, 18.9 to 107.8 mug/ml). The maximum rise occurred within 2 h with two-thirds of the rise occurring within 30 min. During the subsequent 22 h levels dropped to 65.4% of the peak.