Moxalactam epimer disposition in patients undergoing continuous ambulatory peritoneal dialysis

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.

Antimicrobial Treatment of Peritonitis Associated with Continuous Ambulatory Peritoneal Dialysis

A multitude of therapeutic regimens have been proposed for the management of peritonitis associated with continuous ambulatory peritoneal dialysis (CAPD). There are, however, few clinical trials that have evaluated the efficacy of these proposed regimens in a prospective, comparative fashion. This retrospective report is a tabulation of the published data on antimicrobial treatment of CAPD-related peritonitis. The results are presented for combination and mono-drug therapies; Gram-positive bacterial, Gram -negative bacterial and fungal infections; intravenous, oral and intraperitoneal (i.p.) routes of drug administration; various dosages and dosing intervals; and clinical response and relapse rates. The apparent optimal combination regimen for empiric treatment of peritonitis is vancomycin administered in 1 dialysis exchange/week with ceftazidime. This regimen avoids the toxicity associated with the use of aminoglycosides while maintaining effectiveness.

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.

Absorption of intraperitoneal antibiotics

The treatment of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) usually includes the repeated administration of intraperitoneal (ip) antibiotics. The initial segment of this study (15 noninfected CAPD patients) examined the ip administration of four structurally different agents that represent the common types of antibiotics prescribed for peritonitis: an aminoglycoside (tobramycin), a glycopeptide (vancomycin), a beta-lactam (cefamandole), and an oxa-beta-lactam (moxalactam). Subsequently, 16 CAPD patients with peritonitis received either vancomycin (30 mg/kg) or cefamandole (1 g) in two liters of dialysate over a six-hour dwell period. Vancomycin and cefamandole were absorbed more rapidly in patients with peritonitis as indicated by a more rapid decline in dialysate concentrations, and higher serum concentrations that occurred earlier than in the noninfected patients. Although a higher percentage of the ip dose of vancomycin and cefamandole was absorbed during peritonitis, peak serum concentrations at the end of the drug administration dwell period were not significantly different. Numerous factors influence the absorption of ip antibiotics, including the dialysate drug concentration, the dwell period, protein binding, distribution volume, and presence or absence of peritonitis.

Once weekly intraperitoneal therapy for gram-positive peritonitis

The pharmacokinetics and clinical outcome following a 30 mg/kg/2 L intraperitoneal (IP) dose of vancomycin, which was administered once a week for 3 weeks, was studied in ten continuous ambulatory peritoneal dialysis patients with peritonitis. Vancomycin was 91% absorbed following the first dose and rapidly achieved therapeutic serum concentrations, 19 +/- 8 mcg/mL at 1 hour and a peak of 37 +/- 8 mcg/mL at 6 hours. Vancomycin was eliminated slowly with a mean total clearance of 7 +/- 3 mL/min/70 kg and a distribution volume of 1.2 +/- 0.3 L/kg. The resultant mean serum t1/2 over the first week was 184 hours and the mean serum concentration at 168 hours was 10 +/- 4 mcg/mL. Based on the positive clinical outcome (100% cure) among patients with uncomplicated gram-positive peritonitis, the potential use of this alternative vancomycin dosing regimen is proposed.

Comparative study of intraperitoneal and intravenous vancomycin pharmacokinetics during continuous ambulatory peritoneal dialysis

The pharmacokinetic characteristics of vancomycin were investigated in eight patients undergoing continuous ambulatory peritoneal dialysis. A crossover design was used. Four noninfected patients received both a 15-mg/kg (body weight) intravenous dose and a 30-mg/kg intraperitoneal (i.p.) dose. Bioavailability ranged from 0.35 to 0.65 after i.p. administration. i.p. absorption was rapid, with concentrations in serum of 8.8 +/- 6 micrograms/ml noted at 1 h peak values of 30.4 +/- 7 micrograms/ml at 6 h. A slow distribution phase was apparent, with a terminal elimination phase emerging after 12 to 24 h. Vancomycin was eliminated slowly, with a mean total clearance of 5.0 +/- 1.3 ml/min, and concentrations in serum were 7.0 +/- 1.2 micrograms/ml at 168 h. The mean serum half-life was 91.7 +/- 28.1 h, and similar pharmacokinetics were noted after intravenous administration. Subsequently, four patients with catheter-related exit site or tunnel infections received a 30-mg/kg i.p. dose of vancomycin and displayed a similar kinetic pattern. This method of administering vancomycin achieved therapeutic serum and end-dwell dialysate concentrations over a 1-week period, represents a simple, cost-effective therapy which avoids the possibility of infusion-related toxicity, and deserves further investigation in patients with continuous ambulatory peritoneal dialysis-related peritonitis.