Pharmacokinetics of recombinant human erythropoietin in children treated with continuous ambulatory peritoneal dialysis

Use of erythropoiesis-stimulating agents in children with chronic kidney disease: a systematic review

Background

Erythropoiesis-stimulating agents (ESAs) revolutionized the management of anaemia in chronic kidney disease (CKD) when introduced in the late 1980s. A range of ESA types, preparations and administration modalities now exist, with newer agents requiring less frequent administration. Although systematic reviews and meta-analyses have been published in adults, no systematic review has been conducted investigating ESAs in children.

Methods

The Preferred Reporting Items for Systematic Reviews and Meta-analyses statement for the conduct of systematic reviews was used. All available literature on outcomes relating to ESAs in children with CKD was sought. A search of the MEDLINE, CINAHL and Embase databases was conducted by two independent reviewers. Inclusion criteria were published trials in English, children with chronic and end-stage kidney disease and use of any ESA studied against any outcome measure. An assessment of risk of bias was carried out in all included randomized trials using the criteria from the Cochrane Handbook for Systematic Reviews of Interventions. Two tables were used for data extraction for randomized and observational studies. Study type, participants, inclusion criteria, case characteristics, follow-up duration, ESA type and dosage, interventions and outcomes were extracted by one author.

Results

Of 965 identified articles, 58 were included covering 54 cohorts. Six were randomized trials and 48 were observational studies. A total of 38 studies assessed the efficacy of recombinant human erythropoietin (rHuEPO), 11 of darbepoetin alpha (DA) and 3 of continuous erythropoietin receptor activator (CERA), with 6 studies appraising secondary outcome measures exclusively. Recruitment to studies was a consistent challenge. The most common adverse effect was hypertension, although confounding effects often limited direct correlation. Two large cohort studies demonstrated a greater hazard of death independently associated with high ESA dose. Secondary outcome measures included quality of life measures, growth and nutrition, exercise capacity, injection site pain, cardiovascular function, intelligent quotient, evoked potentials and platelet function.

Conclusions

All ESA preparations and modes of administration were efficacious, with evidence of harm at higher doses. Evidence supports individualizing treatments, with strong consideration given to alternate treatments in patients who appear resistant to ESA therapy. Further research should focus on randomized trials comparing the efficacy of different preparations, treatment options in apparently ESA-resistant cohorts and clarification of meaningful secondary outcomes to consolidate patient-relevant indices.

Adsorption of Erythropoietin and Growth Hormone to Peritoneal Dialysis Bags and Tubing

Objective

To study the adsorption of erythropoietin and growth hormone to dialysis bags and tubing.

Design

In vitro study in which radiolabeled erythropoietin and recombinant human growth hormone were added to small-volume (50- and 250-mL) dialysis bags. Recovery was measured after 15-minute dwells. Experiments were performed in triplicate.

Setting

University hospital.

Results

Adsorption of erythropoietin and growth hormone was less than 7%.

Conclusion

Adsorption of erythropoietin and recombinant human growth hormone to dialysis bags and tubing is minimal. This finding provides another argument in favor of intraperitoneal therapy in pediatric peritoneal dialysis.

Increase of the Bioavailabllity of Intraperitoneal Erythropoietin in Children on Peritoneal Dialysis by Administration in Small Dialysis Bags

Objective

To establish the effectivity of administration of erythropoietin intraperitoneally in a small amount of fluid in children with renal anemia on continuous ambulatory peritoneal dialysis (CAPD).

Design

Prospective study in which children with renal anemia on CAPD were treated with erythropoietin intraperitoneally, administered in a specially designed bag containing 50 mL NaCl 0.9%.

Setting

University hospital.

Patients

The patient population consisted of 9 children treated with CAPD and 1 treated with nightly intermittent peritoneal dialysis. The median age was 7.8 years (range 4.1 -15.2). Four of these children had not been treated with erythropoietin before (group A), and 6 had been treated with erythropoietin administered intraperitoneally in 250 mL of dialysis fluid (group B).

Interventions

Patients in group A started on a dose of approximately 300 units/kg per week (group A). Patients in group B received their previous dose. Do sage was adjusted to achieve a target hemoglobin level of 6.5 7.0 mmol/L (104 -112 g/L). Serum ferritin levels and transferrin saturation were monitored and iron supplementation was prescribed in the case of iron deficiency.

Main outcome measures

Weekly erythropoietin dose in relation to hemoglobin level.

Results

In group A, median hemoglobin level rose from 5.3 mmol/L (85 g/L) to 6.6 mmol/L (106 g/L) after 6 months of therapy, whereas the median erythropoietin dose decreased from 266 to 234 U/kg/week. In group B, hemoglobin levels remained stable and median erythropoietin dose decreased from 262 to 194 U/kg/week. One patient in this group, for unknown reasons, never responded to erythropoietin treatment. He was excluded from further analysis. In the remaining 5 patients the median cumulative erythropoietin dose was 3250 U/kg in the 3-month period prior to the start of the study and 2713 in the 3-month period starting 6 months after the beginning of the study. This difference of 17% was statistically significant using a Wilcoxon test (p < 0.05).

Conclusion

Intraperitoneal administration of erythropoietin in a small amount of dialysis fluid leads to a decrease in the required dose.

Intraperitoneal treatment with darbepoetin for children on peritoneal dialysis

To determine the efficacy and safety of intraperitoneal administration of darbepoetin in children with renal anemia on peritoneal dialysis, we conducted a single-arm, retrospective, two-centre study in which children were treated with intraperitoneal darbepoetin at the end of nightly intermittent peritoneal dialysis. Controls were those children treated with intraperitoneal erythropoietin six months before conversion to darbepoetin. Children were converted with the conversion factor 200 units erythropoietin=1 microg darbepoetin. Children who started with darbepoetin, started with 0.45 microg/kg/week. Nineteen children entered the study. The mean age was 6.8 years. Eight children were converted from 201 U/kg/week intraperitoneal erythropoietin to 1.0 microg/kg/week intraperitoneal darbepoetin. They were treated for a median period of 31.5 months. Median darbepoetin dose for an adequate erythropoesis over this period was 0.79 microg/kg/week. All 19 children were treated with darbepoetin for a median period of 13.4 months. The median dose for an adequate erythropoesis over this period was 0.63 microg/kg/week. The peritonitis incidence during this study was once every 25.1 months. Three children developed hypertension; one child developed headache. These complications developed after a rapid increase of hemoglobin concentration. Intraperitoneal administration of darbepoetin is effective and safe for children on peritoneal dialysis.

Erythropoietin mimics ischemic preconditioning

Ischemic preconditioning is a powerful endogenous phenomenon in which brief periods of a sub-toxic ischemic insult induce robust protection against future, lengthy, lethal ischemia. The cardioprotective effects of ischemic preconditioning are manifest in all species studied so far, including humans. The ability to reproduce the cardioprotective effects of ischemic preconditioning with pharmacological agents raises the possibility that a drug may ultimately be introduced into clinical practice to treat human hearts undergoing ischemia/reperfusion. This chapter focuses on erythropoietin (Epo), a drug that has already been approved for humans and is in current use for the treatment of anemia associated with chronic renal failure, HIV infection, cancer patients on chemotherapy, and to reduce allogenic blood transfusion in surgery patients. Several recent studies have suggested that this cytokine possesses properties far beyond its capacity to produce red blood cells such as the ability to protect tissues including brain, kidney and heart against injury caused by ischemia/reperfusion. Cardioprotection conferred by Epo has been shown to be equal in magnitude to that conferred by ischemic preconditioning. However, the underlying mechanisms by which Epo protects the heart against injury caused by ischemia remain unknown.

The management of anemia in pediatric peritoneal dialysis patients. Guidelines by an ad hoc European committee

Anemia is common in chronic renal failure. Guidelines for the diagnosis and treatment of anemia in adult patients are available. With respect to the diagnosis and treatment in children on peritoneal dialysis, the European Pediatric Peritoneal Dialysis Working Group (EPPWG) has produced guidelines. After a thorough diagnostic work-up, treatment should aim for a target hemoglobin concentration of at least 11 g/l. This can be accomplished by the administration of erythropoietin and iron preparations. Although there is sufficient evidence to advocate the intraperitoneal administration of erythropoietin, most pediatric nephrologists still apply erythropoietin by the subcutaneous route. Iron should preferably be prescribed as an oral preparation. Sufficient attention has to be paid to the nutritional intake in these children. There is no place for carnitine supplementation in the treatment of anemia in pediatric peritoneal dialysis patients.

Intraperitoneal erythropoietin in children on peritoneal dialysis: A study of pharmacokinetics and efficacy

The pharmacokinetics and efficacy of intraperitoneal (IP) recombinant human erythropoietin (rHuEPO) were investigated in children undergoing chronic peritoneal dialysis. Eight children were administered a single dose of 100 U/kg of rHuEPO IP with 50 mL of dialysate into a dry peritoneal cavity after nighttime peritoneal dialysis. Serum erythropoietin (EPO) levels were measured at 0, 8, 12, and 24 hours. A mean peak EPO level of 187 mU/mL was obtained at 12 hours. The area under the curve was 5,818 mU/h/mL, and relative bioavailability was similar to that found using subcutaneous (SC) dosing. Nine children completed 11 to 12 weeks of IP rHuEPO therapy. The patients maintained a normal hematocrit (34% +/- 2.3%) with a mean final IP rHuEPO dosage that was not significantly greater than the mean previous SC dosage (IP, 290 +/- 194 U/kg/wk; SC, 279 +/- 126 U/kg/wk; P = not significant). There appeared to be a trend for a slightly increased risk for peritonitis compared with historical controls at our center (relative risk = 3.1; 95% confidence interval, 0.92 to 6.3). IP rHuEPO is effective in children undergoing continuous cycling peritoneal dialysis without requiring increased rHuEPO dosages, but the possibility of an increased risk for peritonitis will need to be further explored.

Erythropoietin in pediatric cardiac surgery: clinical efficacy and effective dose

We assessed the clinical efficacy and determined the effective dose of erythropoietin (EPO) in 48 children scheduled for open heart surgery without blood transfusion. The children were divided into three groups: group 1 (n=21) was treated with 300 U/kg of EPO; group 2 (n=11) was treated with 150 U/kg of EPO; and group 3 (n=16) was not treated with EPO. EPO was administered on the day of hospital admission (6 to 7 days prior to surgery), on the following day, immediately after surgery, and on the following day. Immediately after surgery, the hemoglobin concentration in groups 1 and 2 was significantly higher than that in group 3. The reticulocyte count in groups 1 and 2 was significantly higher than that in group 3. Open heart surgery was completed without transfusion in all 21 patients in group 1 (100%), 10 of 11 in group 2 (90.9%), and 11 of 16 in group 3 (68.8%). EPO caused no adverse reactions. In conclusion, EPO was effective as an adjuvant therapy for open heart surgery without blood transfusion in children. Administration of a relatively high dose of EPO (300 U/kg) seems to be effective for pediatric patients.

In vitro properties and organ uptake of rat band 3 cross-linked erythrocytes

Chemical conditions for cross-linking rat erythrocytes with bis(sulfosuccinimidyl)suberate (BS3) and 3,3' dithiobis(sulfosuccinimidyl propionate) (DTSSP) have been studied. These two cross-linking reagents seem to react with band 3 proteins in rat erythrocyte membrane. Two different conditions have been assayed using different cell/cross-linker concentration ratios. Similar cell volumes were observed in cross-linked rat erythrocytes compared to rat control erythrocytes. Cell yields after cross-linking account for about 65% when a high ratio of cell-to-cross-linker was used. Slightly lower cell yields (about 62%) were obtained when this ratio was reduced. Estimation of band 3 cross-linking by gel electrophoresis revealed a level of cross-linking of around 45% and 50% at the different conditions used. In vivo behavior of these modified rat erythrocytes revealed that they do not circulate, showing a predominant localization in the liver. This effect is evident from the concentration (5 mM BS3 or DTSSP) used. Based on these results, BS3 and DTSSP can be considered as useful tools to cross-link rat erythrocyte band 3 and to target rat erythrocytes to the liver.

Targeting of mouse erythrocytes by band 3 crosslinkers

Chemical conditions of crosslinking mouse erythrocytes with BS3 and DTSSP have been studied. These two crosslinking reagents seem to react with band 3 protein in mouse erythrocytes membrane. Extent of crosslinking is dependent on the concentration of the reagent used. Similar cell volumes were observed in crosslinked erythrocytes with respect to control erythrocytes. In vivo behaviour of these modified erythrocytes revealed prominent targeting of crosslinked erythrocytes to liver. This effect is clearly evident when concentrations of 5 mM BS3 or DTSSP were used and can be dependent of reagent concentration. Consequently, from our results BS3 and DTSSP can be considered as very useful tools to control and modulate targeting of crosslinked erythrocytes.

Recombinant human erythropoietin therapy in children on dialysis

The addition of recombinant human erythropoietin (rHuEPO) to the therapeutic regimen for children with chronic renal failure (CRF) is one of the most important improvements in care in the last 20 years. Anemia had played an important role in the morbidity of chronic dialysis treatment. Before the availability of rHuEPO, repeated erythrocyte transfusions provided incomplete treatment and had significant long-term sequelae. Recombinant erythropoietin treatment resulted in the amelioration of anemia and marked reduction in transfusions. Additional benefits of the correction of anemia with rHuEPO include improvements in exercise tolerance and regression of ventricular hypertrophy. Many rHuEPO-treated patients have had subjective increases in appetite, but there has been no consistent improvement in dietary intake or anthropometric measures. Correction of anemia with rHuEPO has not been shown to improve the growth of children with CRF receiving dialysis. The most significant adverse effects of rHuEPO are the development of iron deficiency and the exacerbation or development de novo of hypertension. RHuEPO treatment has been shown to treat the anemia of CRF in children safely and effectively. In most cases, putative inhibitors of erythropoiesis and blood loss can be overcome. Many of the symptoms previously ascribed to "uremia" have improved with correction of anemia. The full implications of treatment of anemia with rHuEPO will be clearer when the health outcomes for children who never become severely anemic or require transfusions are more completely studied.