Optimizing antimicrobial therapy for gram-positive bloodstream infections in patients on hemodialysis

Polysome Profiling Proves Impaired IL-10 and Caspase-8 Translation in PBMCs of Hemodialysis Patients

Triggered by uremic intoxication, a surplus of inflammatory mediators is present in the serum of hemodialysis (HD) patients. Anti-inflammatory counterbalancing mechanisms initiated by interleukin-10 (IL-10) and caspase-8 (Casp-8) appear to be disturbed. Earlier observations let us suppose that translational rather than transcriptional mechanisms are responsible for this effect. Therefore, we investigated the polysome profiling of isolated PBMCs to study gene-specific mRNAs attached to monosomes and polysomes in HD patients (n = 42), patients with lipid disorder and normal renal function (LD, n = 10) and healthy control subjects (CO, n = 9). CRP (C-reactive protein) as a marker of inflammation was significantly elevated in HD and LD patients compared to CO subjects. NGAL (neutrophil-associated lipocalin), a potential marker of kidney disease and inflammation was increased in HD versus LD and CO. LD patients, however, had significantly higher proteosomal IL-10 and Casp-8 activities. LD and HD are two high cardiovascular risk groups with microinflammation. Lower translational activities of IL-10 and Casp-8 mRNAs in HD may be the result of a weak anti-inflammatory response potentially associated with the uremic immune defect.

Review of vancomycin-induced renal toxicity: an update

In recent times the use of larger doses of vancomycin aimed at curbing the increasing incidence of resistant strains of Staphylococcus aureus has led to a wider report of acute kidney injury (AKI). Apart from biological plausibility, causality is implied by the predictive association of AKI with larger doses, longer duration, and graded plasma concentrations of vancomycin. AKI is more likely to occur with the concurrent use of nephrotoxic agents, and in critically ill patients who are susceptible to poor renal perfusion. Although most vancomycin-induced AKI cases are mild and therefore reversible, their occurrence may be associated with greater incidence of end-stage kidney disease and higher mortality rate. The strategy for its prevention includes adequate renal perfusion and therapeutic drug monitoring in high-risk individuals. In the near future, there is feasibility of renoprotective use of antioxidative substances in the delivery of vancomycin.

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.

Vancomycin pharmacokinetics and pharmacodynamics during short daily hemodialysis

BACKGROUND AND OBJECTIVES

Short daily hemodialysis (SDHD) is an alternative to thrice-weekly HD because of its putative physiologic benefits. The purpose of this study was to investigate the effect of SDHD on the pharmacokinetics and pharmacodynamics of vancomycin.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Six noninfected adults who had anuria and were treated with SDHD were studied and received four dialysis sessions over 4 days. After completion of the first SDHD, each patient received vancomycin 15 mg/kg by intravenous infusion. Blood samples were collected over the ensuing 3 days during each subsequent inter- and intradialytic period. Pharmacokinetic parameters were determined. Serum concentration-time profiles were simulated for four vancomycin regimens with maintenance doses administered after every other SDHD. Area under the serum-concentration time curve (AUC) from 0 to 48 hours, 48 to 96 hours, and 96 to 144 hours were calculated, and Monte Carlo simulations were performed to determine the probability of target attainment at an AUC/minimum inhibitory concentration (MIC) ratio ≥800 for each 48-hour AUC at MICs ranging from 0.5 to 2.0 μg/ml.

RESULTS

Median (range) systemic clearance was 7.2 ml/min (5.3 to 10.0 ml/min), and dialytic clearance was 104 ml/min (94 to 106 ml/min). The steady-state volume of distribution was 55.4 L (34.8 to 77.2 L). At MICs ≤1 μg/ml, probability of target attainment was >90% for each 48-hour AUC when vancomycin was administered as a 20-mg/kg loading dose followed by 10 mg/kg after every other SDHD.

CONCLUSIONS

Vancomycin pharmacokinetic parameters in SDHD are consistent with data from thrice-weekly HD. A loading dose of 20 mg/kg followed by 10 mg/kg after every other SDHD provides adequate exposure for pathogens with MICs ≤1 μg/ml.

Single-dose daptomycin pharmacokinetics in chronic haemodialysis patients

BACKGROUND

Daptomycin has concentration-dependent antibacterial activity against Gram-positive bacteria. Its use is increasing in haemodialysis units. The manufacturer recommends a 4-6-mg/kg dose administered every 48 hrs for patients receiving haemodialysis. However, there are no published data about daptomycin pharmacokinetics and clearance during haemodialysis. The recommended dosing regimen would conflict with asymmetric thrice-weekly haemodialysis, which yields two ~44-hr and one ~68-hr interdialytic periods. This is the first study to evaluate daptomycin pharmacokinetics in haemodialysis patients, assess the extent of daptomycin dialytic removal and model serum concentrations at 44 and 68 hrs.

METHODS

Six otherwise healthy subjects on chronic haemodialysis (55.3 +/- 16.1 years old, three females, 66.2 +/- 14.2 kg) received a single 6-mg/kg dose of daptomycin post-haemodialysis infused over 30 minutes. Serial blood samples were collected for ~44 hrs (pre-next haemodialysis) and throughout the subsequent haemodialysis session with a high permeability haemodialyser. Individual pharmacokinetic parameters determined by compartmental analysis were used to model trough serum concentrations at 44 and 68 hrs with 6-, 8- and 10-mg/kg post-haemodialysis doses.

RESULTS

The haemodialysis session in this trial yielded mean urea and daptomycin reduction ratios of 79.6 +/- 5.8% and 57.6 +/- 9.2%, respectively. Daptomycin half-life was 19.4 +/- 6.5 and 3.8 +/- 1.1 hrs 'off' and 'on haemodialysis', respectively, with minimal rebound 1 hr post-haemodialysis. All modelled trough concentrations at 44 and 68 hrs at all doses exceed typical minimum inhibitory concentration (MIC(90)) values for Staphylococcus aureus and Enterococcus faecalis.

CONCLUSIONS

Daptomycin serum concentrations declined by ~50% after a 4-hr haemodialysis session with a high permeability haemodialyser. A 6-mg/kg i.v. post-haemodialysis thrice-weekly dose should result in sufficient pre-haemodialysis daptomycin serum concentrations even after a 68-hr interdialytic period.

Intradialytic administration of daptomycin in end stage renal disease patients on hemodialysis

BACKGROUND AND OBJECTIVES

Infusion of intravenous antibiotics after hemodialysis (HD) may delay initiation of treatment for the next HD shift. Intradialytic administration of drugs such as vancomycin during the final hour of HD obviates these delays. Daptomycin has potent activity against Gram-positive bacteria, but the manufacturer recommends that the dose be infused after HD ends. This study determined the pharmacokinetics of intradialytically dosed daptomycin in patients with ESRD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective crossover study compared single-dose daptomycin (6 mg/kg, 30-min intravenous infusion) pharmacokinetics administered after HD versus during the last part of HD with high-permeability (HP) and low-permeability (LP) dialyzers to seven patients who had ESRD and were on thrice-weekly HD. Serial blood samples were collected to determine daptomycin serum concentrations and protein binding. Statistical analysis was done using linear mixed model analysis.

RESULTS

The maximum serum concentration observed with a 6 mg/kg post-HD dose was 61.1 +/- 7.6 microg/ml with a mean protein binding of 89.2%. Intradialytic daptomycin administration resulted in reduced maximum serum concentration and area under the curve values that were approximately 12 to 20% lower when administered during HD with LP dialyzers and approximately 35% lower with HP dialyzers.

CONCLUSIONS

Intradialytic daptomycin administration during the last 30 min of HD is feasible, provided that larger dosages are used to compensate for intradialytic drug loss. On the basis of our findings, intradialytic doses of approximately 7 mg/kg (LP) or approximately 9 mg/kg (HP) theoretically should be bioequivalent to 6 mg/kg infused after HD. The calculated dosages are mathematically driven and must be validated in prospective clinical trials.

Cephalosporin-induced neurotoxicity: clinical manifestations, potential pathogenic mechanisms, and the role of electroencephalographic monitoring

OBJECTIVE

To review the clinical manifestations of cephalosporin-induced neurotoxicity, underlying potential mechanisms, role of electroencephalographic (EEG) monitoring, and management of neurotoxicity.

DATA SOURCES

A PubMed search (1970-May 2008) was conducted using search terms such as cephalosporins, neurotoxicity, seizures, and status epilepticus. The search was not limited to the English language and yielded approximately 187 articles.

STUDY SELECTION AND DATA EXTRACTION

Several case reports and case series were included to outline the salient clinical features of cephalosporin neurotoxicity. Laboratory studies investigating the potential mechanisms were also included. Reports outlining the EEG features of cephalosporin neurotoxicity were included and the role of continuous EEG monitoring was extracted. Finally, management strategies of such neurotoxicity are discussed.

DATA SYNTHESIS

Cephalosporin-induced neurotoxicity may manifest in a variety of clinical presentations, ranging from simple encephalopathy or mental status changes to myoclonus, asterixis, seizures, nonconvulsive status epilepticus, as well as coma. Patients who are elderly, those with renal insufficiency, and those with prior neurologic disease may be particularly prone to the neurotoxic effects. The main mechanism of neurotoxicity appears to involve gamma-aminobutyric acid A receptor inhibition, although other mechanisms may be possible. Cephalosporin neurotoxicity may be associated with a variety of EEG manifestations. Treatment mainly involves withdrawal of the offending drug, in addition to hemodialysis in patients with renal failure, and use of benzodiazepines or other anticonvulsants in patients who develop frank status epilepticus. Neurotoxicity can be prevented in high-risk cases with dosage adjustments and monitoring of serum concentrations.

CONCLUSIONS

Knowledge and awareness of the neurotoxic clinical manifestations, EEG findings, and underlying mechanisms are essential for clinicians in identifying and treating this potentially lethal but reversible complication of cephalosporin therapy. Further studies are needed to determine the most appropriate treatment paradigms for patients who develop status epilepticus as a result of cephalosporins.

Drug dosing considerations in alternative hemodialysis

The provision of renal replacement therapy for patients with chronic kidney disease has been reasonably standardized for decades, with thrice-weekly hemodialysis being the standard. Short-daily and nocturnal hemodialysis are 2 new hemodialysis techniques, each are administered 6 to 7 days a week but differ primarily in the duration of the treatment and blood-flow rate. The emergence of these hemodialysis regimens has shown promise in attenuating some of the complications associated with chronic kidney disease. The benefits of these daily regimens are postulated to be a result of enhanced solute clearance and improved extracellular volume management. The improved solute clearance associated with daily hemodialysis is likely to lead to altered dialytic clearance of drugs given to patients receiving these therapies. The purpose of this paper is to review the concepts pertinent to drug removal by hemodialysis and discuss the issues related to these new dialysis techniques and how they may have a impact on drug removal and the design of dosing regimens.