Enhanced clearance of vancomycin by hemodialysis in a child

Pharmacokinetics of Vancomycin in Pediatric Patients Receiving Intermittent Hemodialysis or Hemodiafiltration

INTRODUCTION

Vancomycin is a common antibiotic used to treat hemodialysis (HD) or hemodiafiltration (HDF)-related infections in pediatric patients, but optimal dosing remains unknown. This is the first observational study to characterize the pharmacokinetics and evaluate dosing of vancomycin in this population.

METHODS

Eligible patients received IV vancomycin 10 mg/kg per dose postdialysis followed by a series of serum vancomycin concentrations collected before, immediately after, 1 hour after, and 4 hours after dialysis. The pharmacokinetic parameters were estimated using 1- and 2-compartment models and a nonlinear least-squares algorithm.

RESULTS

Among 42 vancomycin courses in 16 patients, 1 compartment model had the best fit for observed data. The net drug removal was 43 ± 13% (39% for HD and 50% for HDF) from an average 3-hour HD/HDF session. The mean elimination constant was 0.28 h-1 (standard deviation [SD], 0.11 h-1) during the intradialytic period compared with 0.0049 h-1 (SD, 0.004 h-1) when off dialysis. The mean volume of distribution was 0.65 (SD, 0.19) L/kg. Duration of dialysis session and mode of dialysis (HD vs. HDF) were significant predictors of vancomycin pharmacokinetic parameters. Half-life was shorter for HDF compared with HD (2.1 vs. 3.5 hours).

CONCLUSIONS

Based on the simulations, an initial vancomycin dose of 10 mg/kg per dose and redosing postdialysis was optimal to achieve a vancomycin concentration range of 5 to 12 mg/L at 4 hours postdialysis and 24-hour area under the curve over minimum inhibitory concentration of ≥400 hours. Therapeutic drug monitoring is necessary to account for residual variability in vancomycin elimination in pediatric patients receiving HD/HDF.

Status of Hemodialysis of Drugs in 2002

Hemodialysis is a life-sustaining chronic therapy for individuals with end stage renal disease (ESRD). It is also frequently used for days to weeks for patients with acute renal failure who are awaiting the recovery of their kidneys from the acute toxic or traumatic event. Both populations of patients often require complex pharmacotherapeutic regimens, and it is not uncommon for them to be receiving 10 or more concomitant medications. Optimization of care for these patients is dependent on the selection of the most appropriate drug as well as dosage regimen design, which accounts for the influence of hemodialysis therapy on drug disposition. During the last 10 to 15 years there have been several significant changes in the prescribed dose of dialysis and the composition and size of dialyzers available for use. Furthermore, reuse of dialyzers, which was rare in the early 1980s, is now common; it is employed with over 70% of patients with ESRD. The new synthetic dialyzers, which are now used for over 60% of ESRD patients in the United States, are uniformly associated with dramatic improvements in drug removal; dialysis clearance increases of 3 to 10 fold were common for the few drugs evaluated. The influence of these changes in hemodialysis therapy on drug disposition are discussed in a quantitative fashion, and a conceptual framework for drug therapy regimen decision making is presented. For the majority of the drugs reviewed, however, there were no data in the literature regarding dialyzability with currently available dialyzers. The generation of dialyzability data for old and new pharmacotherapeutic agents with state of the art dialysis procedures is clearly needed.

Critical care in uraemic children

The special problems posed by renal disease have to be considered when a uraemic child requires intensive care. This report gives an overview on the problems of dialysis treatment, circulatory support, infectious complications, coagulation disorders and increased intracranial pressure.

Practical aspects in the use of cyclosporin in paediatric nephrology

Many factors must be considered for the effective and safe use of cyclosporin A (CsA) in paediatric nephrology. Detailed knowledge of the variable bioavailability, tissue distribution, and metabolism, as well as causes which lead to their alteration are necessary. Factors which affect the activity of the mixed function oxidase system cytochrome P-450 must be considered, i.e. liver dysfunction and many drugs. Precise knowledge of the CsA determination method and the spectrum of metabolites is essential. In children with renal transplants, a body surface area-related dose will better meet the dose requirements than a body weight related-dose. For drug level monitoring whole blood rather than plasma should be used, and the parent drug level should be the main determinant; elevated metabolite levels may be important in suspected nephrotoxicity or liver dysfunction. Pharmacokinetic profiles are necessary to discover absorption problems or increased CsA clearance rates which necessitate shorter dosing intervals. In children with steroid-dependent minimal change nephrotic syndrome, remission without steroids is maintained as long as CsA is given. The appropriate starting dosage is 150 mg/m2 per day; trough level monitoring is mandatory to prevent nephrotoxicity and to confirm adequate immunosuppressive drug levels which should be 80-160 ng/ml (parent drug level). Although the benefit of CsA has been reported in some cases of lupus erythematosus, its use should be restricted to severe cases only until its efficacy and safety has been confirmed in controlled trials.

Are blood transfusions beneficial in the cyclosporine era?

In patients treated with conventional immunosuppression (azathioprine and prednisone) after renal transplantation, there is a beneficial effect of pre-transplant blood transfusions on graft survival; in patients treated with cyclosporine, this effect may be lost. In 66 children who received living-related donor transplants after donor-specific transfusions (DST) and were treated with azathioprine-prednisone in our center, 1- and 5-year graft survival rates were 99% and 77% respectively. These rates were similar to those reported for children who did not receive DST but were treated with cyclosporine in other centers. There were 634 adult and pediatric recipients of cadaver transplants in our center who were treated with cyclosporine and prednisone (non-sequential therapy, n = 89) or antilymphoblast globulin, azathioprine preduisone, and cyclosporin (sequential therapy, n = 545). When all patients were considered, graft survival rates were higher in transfused than in non-transfused patients at 3-5 years, but in the sequential therapy group, there were no differences in graft survival rates between transfused and non-transfused patients. The results suggest that transfusions do not improve cadaver graft survival in patients receiving optimal cyclosporine therapy and that equally good related donor graft survival can be achieved with DST and conventional immunosuppression or no DST and cyclosporine.