Cefazolin and cephalexin kinetics in continuous ambulatory peritoneal dialysis

A Systematic Review on the Clinical Pharmacokinetics of Cephalexin in Healthy and Diseased Populations

Cephalexin is a first-generation β-lactam antibiotic used in adults and pediatrics to treat various streptococcal and staphylococcal infections. This review aims to summarize and evaluate all the pharmacokinetic (PK) data on cephalexin by screening out all pertinent studies in human beings following the per oral (PO) route. By employing different online search engines such as Google Scholar, PubMed, Cochrane Central, and Science Direct, 23 studies were retrieved, among which nine were in healthy subjects, five in diseased ones, and the remaining were drug-drug, drug-food, and bioequivalence-related. These studies were included only based on the presence of plasma concentration-time profiles or PK parameters, i.e., maximum plasma concentration (Cmax), half-life (t1/2) area under the curve from time 0-infinity (AUC0-∞), and clearance (CL/F). A dose-proportional increase in AUC0-∞ and Cmax can be portrayed in different studies conducted in the healthy population. In comparison to cefaclor, Cmax was recorded to be 0.5 folds higher for cephalexin in the case of renal impairment. An increase in AUC0-∞ was seen in cephalexin on administration with probenecid, i.e., 117 µg.h/mL vs. 68.1 µg.h/mL. Moreover, drug-drug interactions with omeprazole, ranitidine, zinc sulfate, and drug-food interactions for cephalexin and other cephalosporins have also been depicted in different studies with significant changes in all PK parameters. This current review has reported all accessible studies containing PK variables in healthy and diseased populations (renal, dental, and osteoarticular infections, continuous ambulatory peritoneal dialysis) that may be favorable for health practitioners in optimizing doses among the latter.

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

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.

Treatment of Peritonitis in Continuous Ambulatory Peritoneal Dialysis (CAPD) with Intraperitoneal Cefazolin and Gentamicin

Between 1983 and 1988 57 peritonitis episodes in an unselected patient population were initially treated with intraperitoneal cefazolin and gentamicin. The loading dose consisted of 500 mg cefazolin/L dialysate and 40 mg gentamicin/L dialysate. The maintenance dosage was 125 mg cefazolin and 8 mg gentamicin per liter dialysate. Forty-five (78.9%) patients were primarily cured with this regimen (responder group = RG). Twelve patients (21.1 %) did not respond to the initial therapy (nonresponder group = NG). Eight peritonitis episodes in the NG (14.0% of all patients) were caused by tunnel infections and 2 by diverticulitis (3.5%). The cure rate in patients without tunnel infection or bowel disease was 95.7%. A relapse occurred in 2 patients (3.5%). Duration of therapy was assessed by daily white blood cell count (WBC) in the effluent and treatment was discontinued when the WBC was <100/μ1 for 3 days. The mean duration of therapy with cefazolin and gentamicin was 8.1 days in the RG and 6.0 days in the NG. Nonresponders were subsequently treated with a modified antibiotic regimen on an average 11.9 days.

Influence of Continuous Ambulatory Peritoneal Dialysis on Elimination of Drugs

Renal failure delays elimination of many drugs thus prolonging their half lives. By knowing the half life and distribution volume, one can estimate total plasma clearance. When measured values have not been reported, endogenous total plasma clearance can be estimated and compared with peritoneal clearance to determine the effect of CAPD on half life. When peritoneal clearance has not been reported, it can be estimated knowing molecular mass and unbound plasma fraction. Such estimates suggest that elimination kinetics of most drugs are not appreciably affected by CAPD. Compared to those of untreated anuric patients, plasma levels of carbenicillin, ticarcillin, some cephalosporins, all aminoglycosides, vancomycin, sfluorocytosine, amantadine, atenolol, sotalol, timolol, chlorpropamide, theophylline and lithium may be reduced somewhat by CAPD. Thus one should monitor plasma levels of these agents to insure therapeutic concentrations rather than simply following the dosage guidelines for anuric patient.

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.

Treatment in Pd Patients of Peritonitis Caused by Gram-Positive Organisms with Single Daily Dose of Antibiotics

This study was a retrospective case analysis of treatment results of peritonitis in PD patients caused by gram-positive organisms in two different but comparable periods.

Cases were entered, regardless of status of exit site, or whether it was the patient's first or subsequent peritonitis episode.

Failure was defined as either recurrence of peritonitis (with same organism within four weeks of cessation of treatment) or the therapeutic decision to remove the catheter.

Cefazolin used in doses of 1.5 g once a day intraperitoneally (1.0 g if body weight was < 50 kg) with initial tobramycin until culture results became available resulted in a 77% overall cure rate compared to 74% cure in a similar group treated with vancomycin 2.0 g IP weekly (1.0 g if body weight < 50 kg).

Peritonitis caused by methicillin-resistant coagulase-negative staphylococci showed a high failure rate; the change to vancomycin after the initial treatment of these cases would be justified.

The cure rate of peritonitis caused by S. aureus is disappointingly low (58% with vancomycin, 67% with cefazolin). This is due to the high rate of exit-site infections with this organism.

Influence of Peritoneal Dialysate Flow Rate on the Pharmacokinetics of Cefazolin

Objective

To determine the impact of dialysate flow rate (DFR) on cefazolin pharmacokinetics (PK) in peritoneal dialysis (PD) patients.

Methods

A meta-analysis of published reports, identified by MEDLINE search (1966-2002) and other sources, containing information on cefazolin PK data in PD patients was conducted. Data were analyzed based upon low DFR (≤ 5.50 mL/minute) or high DFR (> 5.50 mL/minute). Data available were from North American (NA) ( n = 45) and Singaporean ( n = 10) patients. Complete data sets were available for 33 patients (CDS patients). Data were analyzed with respect to data origin and data set completeness: all patients (ALL), NA, and CDS. Analysis of log-transformed cefazolin PK data was performed to determine coefficient of determination ( r2) between DFR and cefazolin elimination rate constant (kel), clearance total (ClT), and clearance peritoneal (ClPD). Clearance total data were extrapolated to DFR observed in continuous flow PD.

Results

Published literature provided data on 55 PD patients (12 high DFR, 43 low DFR). Regardless of data origin (ALL, NA, or CDS), a prominent coefficient of determination ( p < 0.0001) existed between DFR and all cefazolin PK data except ClPD. The p value for DFR correlation to ClPD was 0.953, 0.011, and 0.036 for ALL, NA, and CDS patients, respectively. Cefazolin ClT and ClPD increased at higher DFRs.

Conclusion

These findings demonstrate that an increased DFR leads to an increased rate of cefazolin clearance in NA PD patients. The impact of Asian descent on cefazolin ClPD warrants further investigation. Clinicians dosing cefazolin in PD patients using a higher DFR than that used to determine cefazolin PK should use increased doses or prescribe lower/comparable DFRs. Data are not yet available for patients prescribed very high DFRs ( e.g., continuous flow PD); extrapolation of our results demonstrates significant influences on clearance and risk for underdosing.

Pharmacokinetics of Intraperitoneal Cefazolin and Gentamicin in Empiric Therapy of Peritonitis in Continuous Ambulatory Peritoneal Dialysis Patients

Objective

The aim of this study was to measure and evaluate the appropriateness of the actual concentrations of serum and dialysate cefazolin and gentamicin in Thai continuous ambulatory peritoneal dialysis (CAPD) patients treated following the International Society for Peritoneal Dialysis (ISPD) 1996 recommendations for the empiric therapy of CAPD-related peritonitis.

Design

Prospective and descriptive study.

Setting

Institutional level of clinical care.

Patients

CAPD-related peritonitis patients were diagnosed by dialysate effluent white cell count of more than 100/mm3and polymorphonuclear leukocytes of at least 50%. There were 18 patients, all at least 15 years of age, entered; all completed the study.

Intervention

In accordance with the ISPD 1996 recommendations, the antibiotic regimen included continuous intraperitoneal (IP) cefazolin and once-daily IP amino-glycoside. Cefazolin was administered as loading and continuous maintenance doses of 500 and 125 mg/L dialysate, respectively. Gentamicin, 0.6 mg/kg body weight, was given IP once daily. Duration of treatment was 120 hours.

Main Outcome Measures

Serum and dialysate effluent samples of the 18 CAPD patients with peritonitis were measured and used for the synthesis of pharmacokinetic equations that could predict drug concentrations at any treatment time.

Results

Following administration according to the ISPD 1996 treatment recommendations, serum cefazolin reached levels higher than the recommended levels (8 mg/mL) at 3.3 minutes after drug administration, and persisted through the 5-day duration of the study. Dialysate cefazolin levels during the studied period also were persistently higher than the recommended values. The peak serum gentamicin levels were lower than the suggested values of 4 mg/mL, whereas the trough serum gentamicin levels were higher than the minimal toxic concentrations (2 mg/mL). Dialysate gentamicin levels were higher than therapeutic concentrations for only 4.75 hours in each day. It was difficult, using pharmacokinetic studies, to adjust the dosage regimen of gentamicin to achieve appropriately therapeutic levels in both serum and dialysate.

Conclusions

The ISPD 1996 recommended dosage of continuous IP cefazolin could be appropriate for the treatment of CAPD-related peritonitis. Once-daily IP gentamicin administration, however, has less therapeutic benefit and should be re-evaluated.

Pharmacokinetics of clindamycin in the plasma and dialysate after intraperitoneal administration of clindamycin phosphoester to patients on continuous ambulatory peritoneal dialysis: an open-label, prospective, single-dose, two-institution study

We evaluated the pharmacokinetics of clindamycin and the dose of clindamycin phosphate necessary to treat peritonitis after intraperitoneal administration of clindamycin phosphate to patients on continuous ambulatory peritoneal dialysis (CAPD). This was an open-label, prospective, single-dose study conducted at the two levels of institutional clinical care in South Korea. Twelve patients (six men and six women; all older than 25 years), mean CAPD duration of 38.2 months with various origins without peritonitis, received 600 mg clindamycin phosphate mixed with only the first 2-L dialysate (1.5% dextrose). The 1.5%, 1.5%, 2.5% and 1.5% dextrose dialysates were serially exchanged every 6 hr. If patients were non-anuric, 24-hr urine samples were also collected. Clindamycin phosphate was incompletely activated to clindamycin in the dialysate. The clindamycin concentration in the dialysate was greater than the effective concentration (5 μg/mL) at 6.87 μg/mL up to 6 hr. So, 600 mg clindamycin phosphate per every 6 hr dialysate is effective for treatment of peritonitis. It has been reported that the clindamycin concentrations in the dialysate may be higher in CAPD patients with peritonitis. Thus, we can expect that intraperitoneal administration of <600 mg clindamycin phosphate per every 6 hr dialysate could be maintained over 5 μg/mL in patients with peritonitis. The transfer of clindamycin was unidirectional from the dialysate to the plasma.

Pharmacokinetics of intermittent intravenous cefazolin and tobramycin in patients treated with automated peritoneal dialysis

There is increasing use of intermittent dosing of antibiotics to treat peritoneal dialysis (PD)-related peritonitis. The disposition of intravenous cefazolin and tobramycin was studied in automated PD (APD) patients. Ten patients were recruited and received a single intravenous dose of cefazolin (15 mg/kg) and tobramycin (0.6 mg/kg). Blood and dialysate samples were collected at the beginning, middle, and end of dwells 1 to 3 (on cycler), and at the end of dwells 4 to 5 (off cycler) for a 24-h period. Baseline and 24-h urine samples were collected. Pharmacokinetic parameters were calculated using a monoexponential model. Cefazolin and tobramycin half-lives were markedly different on cycler than off cycler (cefazolin on cycler : 10.67 +/- 4.66 h; cefazolin off cycler : 23.09 +/- 5.6 h; P = 0.001; tobramycin on cycler : 14.27 +/- 4.53 h; tobramycin off cycler : 68. 5 +/- 26.47 h; P < 0.001). Mean serum and dialysate concentrations were above minimum inhibitory concentrations of susceptible organisms throughout the 24-h period for both drugs with intravenous administration. A model was developed to examine serum and dialysate concentrations after intermittent intraperitoneal administration of 15 mg/kg cefazolin and 0.6 mg/kg tobramycin. Model-predicted intraperitoneal cefazolin provides adequate serum and dialysate concentrations for 24 h. Intermittent intraperitoneal tobramycin doses must be 1.5 mg/kg for one exchange during the first day and then given as 0.5 mg/kg thereafter. It is concluded that the current empiric dosing recommendations for PD-related peritonitis may be adequate for cefazolin (15 to 20 mg/kg); however, tobramycin doses must be changed to 1.5 mg/kg intraperitoneally on day 1, then to 0.5 mg/kg intraperitoneally thereafter in APD patients.

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.

Formulation and release kinetics of cephalexin monohydrate from biodegradable polymeric microspheres

Sustained release cephalexin microspheres have been formulated with poly(L-lactic acid) for intraperitoneal administration. Microspheres were prepared with spray-dried cephalexin by phase separation in organic solvent containing a fixed concentration of polymer, then sieve-sized. Batch-to-batch reproducibility of microsphere size distribution and encapsulation efficiency ( > 95%) were demonstrated. The quality of the microspheres was dependent on the rate of stirring during preparation and was highest as 400 rpm. Scanning electron micrographs revealed approximately spherical shapes and porous surfaces. The release of cephalexin followed second order dissolution model kinetics for multiparticulate systems. The apparent second order rate constant, k2, was lowest for the highest sieve-size fraction (250-425 microns) and varied with drug loading reaching a minimum at 33% w/w. A lower molecular weight PLA of 50 000 produced a faster release of cephalexin from microspheres. Cephalexin was released from microspheres for at least 4 h compared to only 10 min for complete dissolution of an equivalent weight of cephalexin powder, indicating sustained release which may be appropriate in treating localized infections.

Pharmacokinetics of imipenem-cilastatin in patients with renal insufficiency undergoing continuous ambulatory peritoneal dialysis

In six patients with end-stage renal disease, a single bolus of imipenem-cilastatin (500 mg each) was given either intravenously or intraperitoneally in a randomized crossover protocol such that each patient received the drug by both routes at a 2- to 3-week interval. Drug levels in plasma and the peritoneal dialysis fluid were analyzed at frequent intervals, and various pharmacokinetic variables were calculated for a one-compartment open model. Data obtained in the present study suggest that while no significant difference in peak plasma levels or volume of distribution were noted, the following variables were significantly different for imipenem as compared with cilastatin: elimination half-life, total plasma clearance, area under the concentration-time curve, and percent drug excretion in the peritoneal dialysis fluid. The elimination half-life of imipenem (3.28 h) or cilastatin (8.84 h) in our patients was in the same range as observed in patients with minimal renal function undergoing hemodialysis. The dose of imipenem-cilastatin should be reduced appropriately in patients with end-stage renal disease undergoing peritoneal dialysis.

Compatibility of cefazolin and gentamicin in peritoneal dialysis solutions

The compatibility of cefazolin and gentamicin in fluid commonly used for continuous ambulatory peritoneal dialysis (CAPD) was studied. Five admixtures containing cefazolin (75 mg/L and 150 mg/L) and gentamicin (8 mg/L), alone and in combination, were prepared in 1.5% dextrose peritoneal dialysis solution. Solutions were stored for 48 hours at 4 degrees C, 26 degrees C, and 37 degrees C; aliquots for drug assay were obtained at 0, 4, 8, 24, and 48 hours. HPLC and immunofluorescent assays were used to determine cefazolin and gentamicin concentrations, respectively. The cefazolin and gentamicin concentration changes over the study period did not reach statistical significance. Maximal cefazolin and gentamicin losses (12 and 7 percent of the initial concentrations, respectively) were observed at 48 hours in solutions stored at 37 degrees C. No significant differences in concentration changes were observed between combination solutions and solutions containing either cefazolin or gentamicin alone. Cefazolin and gentamicin, alone or in combination, are compatible for at least 48 hours in CAPD solutions.

Disposition of cefotaxime and desacetyl cefotaxime during continuous ambulatory peritoneal dialysis

The disposition of cefotaxime (CTX) and desacetyl cefotaxime (DAC) was studied in eight noninfected patients on continuous ambulatory peritoneal dialysis. Each patient received a single intravenous (i.v.) infusion and an intraperitoneal (i.p.) instillation of 2 g of CTX. Multiple blood and dialysate samples were collected during the 72-h period after drug administration. The half-life, steady-state volume of distribution, and total body clearance of CTX following i.v. administration were 2.2 +/- 1.0 h (mean +/- standard deviation), 0.17 +/- 0.03 liters/kg, and 81.0 +/- 31.0 ml/min, respectively. No significant differences were observed in these parameters after i.p. administration. The continuous ambulatory peritoneal dialysis clearances of CTX and DAC were 1.82 +/- 0.43 and 2.84 +/- 0.70 ml/min, respectively, after i.v. administration. The bioavailability of CTX after i.p. instillation was 74.6 +/- 21.3%. Peak peritoneal dialysate CTX and DAC concentrations of 264.3 and 25.8 mg/liter, respectively, were observed after i.p. dosing. Administration (i.v.) of 2 g every 12 h or i.p. instillation of 2 g every 24 h may be used for the treatment of i.p. infections with highly susceptible organisms (MIC less than 1.0 microgram/ml).

Pharmacokinetics of intravenous and intraperitoneal ceftriaxone in chronic ambulatory peritoneal dialysis

The kinetics of ceftriaxone was investigated in 8 patients without infection, who were receiving continuous ambulatory peritoneal dialysis (CAPD). Ceftriaxone 1 g was injected i.v. and 1 g was given intraperitoneally in the CAPD fluid during a 4-h dwell time. Ceftriaxone was assayed by HPLC. After intravenous administration, the kinetic parameters of ceftriaxone were: plasma t1/2, 12.3 h, total plasma clearance, 14.0 ml/min, volume of distribution at steady state 0.18 l/kg, and peritoneal clearance 0.59 ml/min. Over 72 hours only 5.5% of the dose was eliminated by the peritoneal route. After intraperitoneal administration, ceftriaxone rapidly appeared in serum; the absorption t1/2 was 1.1 h and the mean peak concentration was 38.8 micrograms/ml. The absorption of ceftriaxone from the peritoneal space was 39%. A single 1.0 g IP dose led to serum and dialysate concentrations of ceftriaxone above the minimum inhibitory concentration for susceptible pathogens for 24 hours.

Pharmacokinetics of intravenous and intraperitoneal moxalactam in chronic ambulatory peritoneal dialysis

The kinetics of moxalactam has been investigated in 10 subjects undergoing continuous ambulatory peritoneal dialysis (CAPD). A single 1 g dose was injected i.v. and a 1 g dose was given intraperitoneally in the CAPD fluid during a 4 h dwell-time. Moxalactam was assayed by HPLC. After i.v. injection, the serum kinetics of moxalactam were: plasma t 1/2 = 17.9 h; volume of distribution at steady-state, 0.27 l/kg; total plasma clearance, 12.8 ml/min; peritoneal clearance, 2.1 ml/min. Dialysate moxalactam concentrations rose rapidly but only 20% of the dose was eliminated by the peritoneal route. After intraperitoneal instillation, moxalactam appeared in the serum rapidly and the peak serum concentration ranged from 21 to 49 micrograms/ml after between 4 and 5 h. The absorption of moxalactam from the peritoneal space was 57 +/- 16%. The data suggest that moxalactam has bidirectional exchange characteristics through the peritoneal membrane. Instillation of moxalactam in CAPD fluid may permit rapid absorption and the appearance of a therapeutic serum concentration.

Cefmenoxime kinetics during continuous ambulatory peritoneal dialysis

The kinetics of the aminothiazolyliminomethoxy cephalosporin, cefmenoxime, were determined after a 30 min intravenous infusion of 15 mg/kg body weight in 6 adult subjects undergoing continuous ambulatory peritoneal dialysis. Concentrations of cefmenoxime in serum, urine and dialysate were determined by high-pressure liquid chromatography. The mean peak serum concentration was 92.8 +/- 11.6 micrograms/ml and the harmonic mean for the elimination half-life was 5.46 h. The volume of distribution at steady-state was 14.60 +/- 3.01 l/kg. Total body clearance of the drug was 31 +/- 7.7 ml/min with 8 +/- 5% and 5.75 +/- 2.72% of the administered dose being eliminated by renal and peritoneal clearance, respectively. Peritoneal clearance for all exchanges (n = 24) was 1.93 +/- 68 ml/min. These data suggest that peritoneal losses of this drug are minimal and doses conventionally employed in advanced renal failure can be utilized in the management of systemic infections.

Serum and dialysate concentrations of cephalexin following repeated dosing in CAPD patients

Oral cephalexin, 1 to 2 g daily for 3 days, was given to six stable, noninfected patients receiving maintenance continuous ambulatory peritoneal dialysis (CAPD). The peak serum concentration after a 2 g initial dose was between 73 and 123 mg/L. On the second and third day in five patients who received a 2 g daily oral dose, the serum concentrations were between 35 and 118 mg/L in serum obtained 1 to 1.5 hours after the dosing. Similar serum concentrations were seen in one patient who only received a 1 g oral dose on the second and third day. Cephalexin concentrations in the peritoneal dialysate reached a peak on the first day between 4 to 14 hours after the dose and were between 31 to 78 mg/L. During the second and third day, the highest cephalexin concentration was 118 mg/L and the lowest was 12 mg/L. The data are consistent with the feasibility of oral cephalexin for treatment of CAPD-associated peritonitis with microorganisms that are sensitive to these levels of cephalexin.

Moxalactam kinetics during continuous ambulatory peritoneal dialysis after intraperitoneal administration

Moxalactam kinetics during continuous ambulatory peritoneal dialysis (CAPD) was followed in eight patients after a single intraperitoneal dose of 1 g. Approximately 60% of the dose was absorbed after a dwell time of 4 h. Dialysis solutions were exchanged at 4-h intervals with an overnight dwell of 8 h. The mean (+/- standard deviation) elimination half-life was 13.2 +/- 2.9 h, and the mean apparent volume of distribution was 0.22 +/- 0.08 liters/kg. Mean total clearance was 11.5 +/- 2.4 ml/min, with a mean dialysis clearance of 2.3 +/- 0.5 ml/min. The maximum concentration in plasma ranged from 24.5 to 54.1 micrograms/ml. Moxalactam concentrations in the peritoneal dialysis fluid were above 80 micrograms/ml during the first exchange and above 2 micrograms/ml for a further three exchanges. A suggested intraperitoneal dose regimen for patients undergoing CAPD is 1 g initially, followed by 15 to 25% of the recommended dose for normal patients given at the same time intervals, or 30 to 50% of the recommended dose at twice the usual intervals. Moxalactam is suggested for initial treatment of peritonitis in CAPD patients who do not have ready access to the antibiotic of choice.

Effect of hemodialysis and peritoneal dialysis on aztreonam pharmacokinetics

Aztreonam, a new monobactam, will be widely used because of its broad aerobic gram-negative bacterial coverage and its apparent low risk of allergic phenomena in penicillin/cephalosporin-sensitive patients. We examined aztreonam kinetics in patients during hemodialysis and in the interdialytic period and in patients on continuous ambulatory peritoneal dialysis (CAPD), and related aztreonam to urea clearance (CL). In hemodialysis patients, aztreonam serum half-life was 7.9 hr between and 2.7 hr during dialysis sessions. CLserum, CLrenal, and CLother were 24.4, 0.5, and 23.9 ml/min, respectively, during the interdialytic period. Four hours of dialysis removed 38.2% (range, 27 to 58%) of antibiotic. CL of aztreonam by hemodialysis was 36.6 to 43.2 ml/min, 50 to 77% greater than interdialytic CL. CL of urea by hemodialysis was 112.4 to 115.6 ml/min; CLaztreonam/CLurea ratio was 0.28 to 0.33 during the hemodialysis sessions. During CAPD, aztreonam serum half-life after intravenous dosing was 7.1 hr; dialysate recovery, 9.7% of the dose; CLserum, CLrenal, CLperitoneal dialysis, and CLother were 23.8, 0.5, 2.1, and 21.3 ml/min, respectively. CLurea by CAPD was 6.5 ml/min. Thus, CLaztreonam during CAPD was 32% of CLurea. Aztreonam was detectable in dialysate at 48 hr (eight exchanges) after peritoneal administration in the first exchange. Hemodialysis and CAPD patients given aztreonam treatment should receive the standard dose of aztreonam as a loading dose, followed by one-fourth the loading dose at standard dose intervals. Hemodialysis patients should receive a supplemental dose equal to half their usual maintenance dose immediately after each dialysis session. For CAPD patients with peritonitis due to susceptible organisms, a 1-g i.v. loading dose followed by a 0.5-g i.p. dose every 6 hr is suggested. In any individual patient undergoing hemodialysis or CAPD, the relationship between CLurea and CLaztreonam should allow appropriate antibiotic dose adjustment.

Pharmacokinetic aspects during continuous ambulatory peritoneal dialysis: a literature review

Since its introduction some years ago continuous ambulatory peritoneal dialysis (CAPD) has proved to be a valuable alternative to haemodialysis in the treatment of uraemia. Factors contributing to the transport of solutes through the peritoneal membrane are discussed and the literature concerning the pharmacokinetic aspects of CAPD is reviewed.

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.

Pharmacokinetics of common antibiotics used in continuous ambulatory peritoneal dialysis

To establish therapeutic guidelines for the use of antibiotics in patients receiving continuous ambulatory peritoneal dialysis (CAPD), we studied the single-dose pharmacokinetics of cefazolin, tobramycin, and vancomycin given intravenously (IV) and intraperitoneally (IP) as well as cephalexin given orally. By the IV or oral route, the antibiotics exhibited half-lives similar to those described in nondialysed, functionally anephric patients. CAPD accounted for only a negligible fraction of the total body clearance when the drugs were given by the IV route. However, when given IP, the drugs were promptly absorbed and achieved therapeutic serum concentrations. The kinetic principle of superposition was applied to predict plasma concentrations after repetitive IP dosing. Therapeutic guidelines are provided.

Pharmacokinetics of ceftizoxime in patients undergoing continuous ambulatory peritoneal dialysis

The pharmacokinetics of ceftizoxime were studied in 12 patients on continuous ambulatory peritoneal dialysis. After a 3-g intravenous dose, the steady-state volume of distribution was 0.23 +/- 0.05 liter kg-1, with an elimination half-life of 9.7 +/- 5.1 h. The peritoneal clearance of ceftizoxime (2.8 +/- 0.7 ml min-1) contributed modestly to the overall serum clearance of the drug (17.1 +/- 7.4 ml min-1) and was greater than the renal clearance (0.8 +/- 0.8 ml min-1). The peritoneal concentration rose to 91 +/- 29 micrograms ml-1 at 6 h, which was 0.61 +/- 0.17 of the serum concentration. A 3-g intravenous dose of ceftizoxime given every 48 h would result in adequate activity against most susceptible organisms, but more frequent dosing may be necessary for less susceptible organisms.