Pharmacokinetics of recombinant human erythropoietin applied subcutaneously to children with chronic renal failure

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.

Optimal care of the pediatric end-stage renal disease patient on dialysis

This manuscript is an effort on behalf of the American Society of Pediatric Nephrology to provide recommendations designed to optimize the clinical care of pediatric patients with end-stage renal disease (ESRD). Although many of the recommendations are evidenced-based with the supporting data being derived from a variety of sources, including patient registries, others are opinion-based and derived from the combined clinical experience of the authors. In all cases, it is recommended that the decision to initiate dialysis should be made only after an assessment of a combination of biochemical and clinical characteristics. Irrespective of the choice of dialysis modality (hemodialysis v peritoneal dialysis), dialysis efficacy should be measured regularly, and the dialysis prescription should be designed to achieve target clearances. Attention to dialysis adequacy, control of osteodystrophy, nutrition, and correction of anemia is mandatory, because all may influence patient outcome in terms of growth, cognitive development, and school performance. Finally, the availability of a multidisciplinary team of pediatric specialists is desirable to provide all facets of pediatric ESRD care, including renal transplantation, in an optimal manner. Future clinical research efforts intended to address topics such as dialysis adequacy, anemia management, and growth should be encouraged.

Management of end-stage renal disease in children

OBJECTIVE

To review the medical literature on management of end-stage renal disease (ESRD) and its complications in the pediatric patient.

DATA SOURCES AND STUDY SELECTION

MEDLINE searches (1970-1997) of the English-language literature. Clinical trials and reviews of drug therapy management were included, and bibliographies were reviewed for relevant articles.

DATA SYNTHESIS

Principles of renal replacement therapy in children have been expanded to include maintenance of fluid and electrolyte balance and to manage the complications of ESRD in children. Types of renal replacement and their complications are reviewed. Complications of ESRD are reviewed with emphasis on drug therapy management of anemia of chronic renal failure, growth retardation, and hypertension. A discussion of the use of vitamins and supplements to maintain bone and mineral homeostasis is provided, and specific recommendations for vaccination of children with ESRD are given.

CONCLUSIONS

Children with end-stage renal failure present a unique challenge to the pharmacist. Renal replacement therapy for children with ESRD involves some form of dialysis and an intensive medication regimen. Complications must be treated with appropriate drug therapy. Drug therapy must be monitored closely for dosage adjustment, clinical response, drug interactions, and toxicity. Patients and families must receive continuous education and follow-up to encourage compliance. The pharmacist must work closely with the healthcare team to optimize drug therapy and improve patient education and compliance.

Pharmacokinetics of recombinant human erythropoietin in children with chronic renal failure

Basal erythropoietin (Epo) levels and single dose-pharmacokinetics of recombinant human erythropoietin (rhuEpo) were investigated in 8 predialysis (PD) patients (mean age 11.6 +/- 1.4 years) and in 8 patients on continuous ambulatory peritoneal dialysis (CAPD) (mean age 12.7 +/- 0.6 years). Basal Epo levels were found to be 1.0 +/- 0.0 mu/ml in PD group, 1.6 +/- 0.7 mu/ml in CAPD group and 8.5 +/- 1.8 mu/ml in control group. Following administration of 50 mu/kg rhuEpo (s.c.) serum Epo concentration (Cmax) was 23.2 +/- 2.5 mu/ml in 18.5 +/- 2.6 hours (tmax) in PD patients and 9.9 +/- 0.8 mu/ml in 26.8 +/- 7.7 hours in CAPD patients. Mean elimination half-lives (t1/2) were 13.3 +/- 1.9 hours and 13.5 +/- 3.0 hours in PD patients and CAPD patients, respectively. The volume of distribution (Vd) was 840.0 +/- 100.0 ml/kg; the clearance (Epo Cl) was 37.0 +/- 5.5 ml/kg/hour in PD patients. These values were significantly lower in PD patients than in CAPD patients (p < 0.05) (Vd; 1500 +/- 240.0 ml/kg; Epo Cl 110 +/- 30.0 ml/kg/hour). During the course of CAPD, more efficient clearance of uraemic toxins that inhibit erythropoiesis and more rapid extraction of erythropoietin by erythroid precursors may cause higher Vd in CAPD patients than in PD patients.

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.

Subcutaneous recombinant erythropoietin in preterminal renal insufficiency

Recombinant human erythropoietin was given to eight children and adolescents with stable chronic renal failure in the predialysis state. The hormone was administered subcutaneously, twice weekly for 12 weeks, at a starting dose of 50 U/kg per week. The dosage was adapted every 4th week. Target haemoglobin was 10.5-11.5 g/dl, and the target haematocrit 32%-35%. Baseline haemoglobin levels of 8.20 +/- 0.93 g/dl increased to 9.17 +/- 1.10, 10.38 +/- 1.18 and 11.19 +/- 0.84 g/dl (mean +/- SD) after 4, 8 and 12 weeks respectively. Serum ferritin levels decreased progressively despite iron supplementation. No side-effects were observed: creatinine clearances remained stable, blood pressure did not increase and none of the patients displayed either convulsions or thrombotic features. The study shows that subcutaneous recombinant human erythropoietin is both effective and safe in anaemic children and adolescents with chronic renal insufficiency.

Treatment of renal anemia by subcutaneous erythropoietin in children with preterminal chronic renal failure

Eleven children aged 0.6-17 years with preterminal chronic renal failure and anemia (mean serum creatinine concentration 4.8 mg/dl; mean hemoglobin concentration 7.9 g/dl) were treated with sc injections of recombinant human erythropoietin (EPO, initial dose 150 U/kg/week) over a mean period of 13 months. When a target hemoglobin concentration of 11.5-13.5 g/dl was reached, the dose was adapted. Iron deficiency was corrected. Hemoglobin concentration increased by > 2 g/dl in all patients within 14-119 (mean 45) days. The last maintenance dose ranged between 75 and 300 (mean 133) U/kg/week. No major adverse effects were observed, except for hypertension which occurred in about half of the patients and necessitated interruption of EPO in one child with advanced renal failure. Additional antihypertensive drugs were given to five patients. Body height increased in two patients by 0.6 and 1.3 SDS/year, respectively. In six patients with a mean observation period of 14 months before and 16 months after the start of EPO, the mean slope of the reciprocal serum creatinine concentration curve improved slightly (p = 0.05). The proposed schedule appears to be safe for the treatment of renal anemia in most pre-dialysis patients. Frequent monitoring of hemoglobin, blood pressure, serum creatinine and ferritin is required.