Intraperitoneal Administration of Recombinant Human Erythropoietin

Objective

To determine the efficacy and safety of intraperitoneal administration of recombinant human erythropoietin (rHuEPO) in continuous ambulatory peritoneal dialysis (CAPD) patients compared to subcutaneous rHuEPO.

Design

Prospective analysis of an open, nonrandomized investigation.

Setting

Outpatient CAPD clinics in two university hospitals.

Patients

Nine adult CAPD patients receiving rHuEPO intraperitoneally and 8 patients receiving rHuEPO sub-cutaneously.

Intervention

One hundred units of rHuEPO per kilogram of body weight were administered three times a week for 8 weeks or until the target hematocrit of 35% was reached. Thereafter, dosages of rHuEPO were adjusted for response. Intraperitoneal rHuEPO was administered in 1 L of dialysis solution during the night.

Measurements

Efficacy was assessed by measuring the increase in hemoglobin. Tolerance was assessed by monitoring side effects.

Results

In the first 8 weeks of treatment hemoglobin concentration increased from 64.5±12.9 glL to 98.3±16.1 g/L (p<0.0005) in the intra peritoneally treated group. In the subcutaneously treated group hemoglobin increased significantlyfaster (p<0.05) from 72.5±4.8 g/L to 119.2±11.3 g/L (p<0.0005) in the same period. Antihypertensive medication had to be increased or instituted in most of the patients in both groups. The incidence of peritonitis in the intraperitoneally treated group was not increased when compared to the pretreatment incidence.

Conclusions

Subcutaneously administered rHuEPO is superior to intraperitoneally administered rHuEPO with regard to the required dosages. However, the results of this study show that intraperitoneal administration of rHuEPO might be a convenient and safe alternative when subcutaneous administration is undesirable.

Increased Response to Subcutaneous Erythropoietin on Type I Diabetic Patients on Capd: Is There a Synergistic Effect with Insulin?

Objective

To evaluate the effect of subcutaneous erythropoietin (SC EPO) on the treatment of anemia in diabetic and nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients.

Design

A resistance index was designed for measuring the relative EPO response, dividing EPO dose (U/kg/ week) by the hemoglobin (Hb) increment with respect to the basallevel.

Patients

Eleven nonselected type I diabetic patients using subcutaneous insulin compared with 16 nondiabetic controls, all on CAPD therapy.

Results

The two groups showed similar mean baseline hemoglobin levels (7.4 D- l and 7.7 non-D, g/dL). There was a statistically significant lower resistance index for diabetics (13.8±9.7 U/kg/g Hb increment) compared to nondiabetic (55.8±128, p < 0.001). Multivariate analysis confirmed an independent association between diabetes and resistance index. The response to EPO was slightly better among those diabetic patients with lower levels of serum parathyroid hormone (iPTH) (PTH-resistance index, correlation coefficient, r = 0.7, p < 0.05). No other differences, apart from the use of subcutaneous insulin, were found between diabetics and controls. Although diabetic patients had an increased response to EPO, they had no more frequent side effects than nondiabetics.

Conclusions

According to our results, we suggest that factors related to insulin-dependent diabetes seem to be involved in a favorable response to SC EPO. Hyperinsulinemia derived from subcutaneous use of insulin might act as a comitogen with the induced increments of serum erythropoietin.

The Pharmacokinetics of Intraperitoneal Erythropoietin Administered Undiluted Or Diluted in Dialysate

+ Objective

To compare the bioavailability of intraperitoneal erythropoietin (EPO) administered undiluted versus diluted in 2 L of dialysis fluid.

+ Design

Group 1 patients received one dose of EPO, 400 Ulkg BW given with vehicle only. This dwelled for 8 hours after which 2 L of dialysate were infused. Group 2 patients received the same dose of EPO diluted in 2 L of dialysate which dwelled for 8 hours. Both groups resumed their CAPD regimen after the first 8 hours. Blood levels of EPO were measured for 24 hours in both groups.

+Setting

The Home Peritoneal Dialysis Unit, Toronto Hospital, Western Division.

+ Patients

The participants were on CAPD for at least three months, free of peritonitis, and had no abnormalities of peritoneal transport. Three patients took part in both arms of the study, and there were 6 patients altogether in each group.

+ Results

When EPO was administered undiluted, there was a greater than ninefold increase in bioavailability of the hormone as measured by the area under the curve (AUC), compared to when the same dose was diluted in 2 L of dialysis fluid.

+ Conclusions

The previous studies that reported low bioavailability of intraperitoneal EPO used the hormone diluted in dialysate. The current findings suggest that if EPO is given in the dry peritoneal cavity, the bioavailability is greatly improved and may be clinically effective. Intraperitoneal instillation may prove to be an alternative route for EPO in the peritoneal dialysis patient unable or unwilling to receive subcutaneous injections. We are currently studying the effectiveness of undiluted intraperitoneal EPO in CAPD patients.

Increased Response to Subcutaneous Erythropoietin on Type I Diabetic Patients on CAPD: Is There a Synergistic Effect with Insulin?

Objective

To evaluate the effect of subcutaneous erythropoietin (SC EPO) on the treatment of anemia in diabetic and nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients.

Design

A resistance index was designed for measuring the relative EPO response, dividing EPO dose (U/kg/ week) by the hemoglobin (Hb) increment with respect to the basallevel.

Patients

Eleven nonselected type I diabetic patients using subcutaneous insulin compared with 16 nondiabetic controls, all on CAPD therapy.

Results

The two groups showed similar mean baseline hemoglobin levels (7.4 D- l and 7.7 non-D, g/dL). There was a statistically significant lower resistance index for diabetics (13.8±9.7 U/kg/g Hb increment) compared to nondiabetic (55.8±128, p < 0.001). Multivariate analysis confirmed an independent association between diabetes and resistance index. The response to EPO was slightly better among those diabetic patients with lower levels of serum parathyroid hormone (iPTH) (PTH-resistance index, correlation coefficient, r = 0.7, p < 0.05). No other differences, apart from the use of subcutaneous insulin, were found between diabetics and controls. Although diabetic patients had an increased response to EPO, they had no more frequent side effects than nondiabetics.

Conclusions

According to our results, we suggest that factors related to insulin-dependent diabetes seem to be involved in a favorable response to SC EPO. Hyperinsulinemia derived from subcutaneous use of insulin might act as a comitogen with the induced increments of serum erythropoietin.

Hematocrit Values in the CAPD/CCPO Population: A Report of the National CAPO Registry

A survey of the National CAPD Registry population was conducted to assess the distribution of hematocrit levels in a large group of peritoneal dialysis patients, to characterize the anemia of the population, and identify factors which relate to variation in hematocrit levels. A random sample of 812 patients was selected from the Registry population. Information was provided on 608 patients. Characteristics of sampled patients were similar to the Registry population as a whole. The mean hematocrit level in this cohort was 29.4% and the median was 29%. Recent peritonitis, time on CAPD, folate therapy, androgen therapy, and iron therapy had no obvious influence on hematocrit distributions. Significantly higher hematocrits were seen in males, whites, and patients with polycystic kidney disease. Significantly lower hematocrits were seen in surgically anephric patients and in patients who had received transfusions 60 days before the survey. Eighty-nine percent of patients had not received a transfusion 60 days prior to the survey. Some patients, especially those with hematocrits below the median, might benefit from recombinant erythropoietin therapy.

Efficient Monthly Subcutaneous Administration of Darbepoetin in Stable CAPD Patients

Background

Although subcutaneous administration of recombinant human erythropoietin (rHuEPO) in continuous ambulatory peritoneal dialysis (CAPD) patients is a widely accepted recommendation, the lowest possible frequency of an efficient dosing regimen remains controversial. Darbepoetin alpha, a new erythropoiesis-stimulating protein with a threefold longer serum half-life compared with rHuEPO, has greater in vivo potency and can be administered less frequently to obtain the same biological response. This study assessed the efficacy of darbepoetin administered once monthly in the treatment of anemia in CAPD patients.

Patients and Methods

In this single-center, prospective cohort study, 11 stable CAPD patients (5 males, 6 females; mean age 68.8 ± 14.1 years; mean duration on peritoneal dialysis 31.6 ± 13 months) maintained average hemoglobin and hematocrit levels of 12.09 ± 1.29 g/dL and 37.29% ± 3.58%, respectively, while receiving a mean weekly maintenance dose of epoetin alfa of 129 IU/kg. These same patients were assigned to receive the equivalent weekly darbepoetin dose once monthly for 24 consecutive weeks. Hematological response, iron status (transferrin saturation, serum ferritin levels), C-reactive protein (CRP), and the patients’ biochemical profiles were evaluated monthly.

Results

During the monthly administration of darbepoetin, mean serum levels of Hb and Hct were 12.17 ± 1.28 g/dL and 37.1% ± 1.19% respectively. No statistically significant difference was apparent between the previous and monthly dosing values (12.09 ± 1.29 vs 12.17 ± 1.28 g/dL, p = 0.769, and 37.29% ± 3.58% vs 37.1% ± 1.19%, p = 0.752). Transferrin saturation levels as well as serum ferritin levels also remained unchanged (30.4% ± 8.6% vs 30.1% ± 9.4%, NS, and 556 ± 212 vs 621 ± 234 ng/mL, respectively, NS).

Conclusion

These results indicate that darbepoetin alfa can be effectively given subcutaneously at monthly intervals for the treatment of anemia in stable CAPD patients. However, more studies are needed to validate the long-term efficacy of this monthly subcutaneous administration.

Erythropoietin in Continuous Ambulatory Peritoneal Dialysis: Experience with Subcutaneous Administration

Experience in the use of subcutaneous erythropoietin (EPO) in 32 continuous ambulatory peritoneal dialysis (CAPD) patients is presented. All patients were treated with oral iron supplements. The total and mean I SD durations of EPO treatment were 466 weeks and 14.6±10.1 weeks respectively. Twenty -two patients started treatment with normal or elevated iron stores; 10 had an initial iron saturation <20%. The initial hematocrit was 23.8±3.7%. Thirteen patients reached a steady -state hematocrit by the end of the study period, when the mean I SD hematocrit for all32 patients was 34.1±3.6%. All patients responded to EPO. The initial dose of EPO was 147.1 ± 53.8 U/kg/week. Maintenance dose was 72±36 U/kg/week.

Hematocrit Influence on Peritoneal Dialysis Effectiveness during Recombinant Human Erythropoietin Treatment in Patients with Chronic Renal Failure

Seven intermittent peritoneal dialysis (IPD) patients were investigated before and after correction of anemia with recombinant human erythropoietin (r-HuEPO). When hematocrit exceeded 300/0, the peritoneal equilibration test was performed at 1, 2, 4, 8 hours.

Correction of anemia was associated with a mean value Increment In creatinine and phosphate clearance In 1 and 2-hour dwells. Differences In clearance of sodium, potassium, and urea In protein loss and glucose absorption before and after r-HuEPO therapy were not statistically significant.

Increased creatinine and phosphate clearance during short dwells can be effected in IPD patients.

Subcutaneous Recombinant Human Erythropoietin in Hemodialysis and Continuous Ambulatory Peritoneal Dialysis

We compared the effect of twice weekly subcutaneous recombinant human erythropoietin (SC rHuEPO) In two groups of patients treated with a starting dose of 80 U/kg body weight/week: group I, 7 hemodialysis (HD) patients; group II, 8 continuous ambulatory peritoneal dialysis (CAPD) patients. In a third group (group III) of 4 patients transferred from HD to CAPD with anemia previously corrected with Intravenous (IV) rHuEPO, we studied the changes In the maintenance SC dose to maintain the same hemoglobin.

In groups I and II the mean SC doses required to correct anemia and to maintain hemoglobin/hematocrit levels were similar; the mean time for the correction of anemia was significantly longer In HD patients (p=0.032). In group III the maintenance SC rHuEPO does was reduced to more than 50% at 12 weeks of CAPD.

Subcutaneous rHuEPO Is effective In reversing anemia in HD and CAPD patients, but It takes longer to correct anemia In HD with the same initial SC rHuEPO low dose. CAPD patients need lower doses of SC rHuEPO than HD patients in IV therapy to maintain the same hemoglobin levels.

Novel process of intrathymic tumor-immune tolerance through CCR2-mediated recruitment of Sirpα+ dendritic cells: a murine model

Immune surveillance system can detect more efficiently secretory tumor-specific antigens, which are superior as a target for cancer immunotherapy. On the contrary, immune tolerance can be induced in the thymus when a tumor antigen is massively secreted into circulation. Thus, the secretion of tumor-specific antigen may have contradictory roles in tumor immunity in a context-dependent manner. However, it remains elusive on the precise cellular mechanism of intrathymic immune tolerance against tumor antigens. We previously demonstrated that a minor thymic conventional dendritic cell (cDC) subset, CD8α⁻Sirpα⁺ cDCs, but not the major subset, CD8α⁺Sirpα⁻ cDCs can selectively capture blood-borne antigens and crucially contribute to the self-tolerance. In the present study, we further demonstrated that Sirpα⁺ cDCs can capture a blood-borne antigen leaking inside the interlobular vascular-rich regions (IVRs). Blood-borne antigen selectively captured by Sirpα⁺ cDCs can induce antigen-specific Treg generation or negative selection, depending on the immunogenicity of the presented antigen. Furthermore, CCR2 expression by thymic Sirpα⁺ cDCs and abundant expression of its ligands, particularly, CCL2 by tumor-bearing mice prompted us to examine the function of thymic Sirpα⁺ cDCs in tumor-bearing mice. Interestingly, tumor-bearing mice deposited CCL2 inside IVRs in the thymus. Moreover, tumor formation induced the accumulation of Sirpα⁺ cDCs in IVRs under the control of CCR2-CCL2 axis and enhanced their capacity to take up antigens, resulting in the shift from Treg differentiation to negative selection. Finally, intrathymic negative selection similarly ensued in CCR2-competent mice once the tumor-specific antigen was secreted into bloodstream. Thus, we demonstrated that thymic Sirpα⁺ cDCs crucially contribute to this novel process of intrathymic tumor immune tolerance.

Pharmacokinetic and toxicity study of intravitreal erythropoietin in rabbits

AIM

To study the pharmacokinetics and toxicity of intravitreal erythropoietin (EPO) for potential clinical use.

METHODS

For toxicity study, 4 groups (60 rabbits) with intravitreal injection (IVit) of EPO were studied (10 U, 100 U, or 1,000 U) per eye for single injection and 0.6 U/eye (the designed therapeutic level in rabbits) for monthly injections (6X). Eye examination, flash electroretinogram (ERG), and fluorescein angiography (FA) were carried out before and after injection. The rabbits were killed for histological study at different intervals. For the pharmacokinetic study, after IVit of 5 U EPO into left eyes, 44 rabbits were killed at different intervals, and the EPO levels in vitreous, aqueous, retina and serum were analyzed by enzyme-linked immunosorbent assay.

RESULTS

At all of the time points examined, the eyes were within normal limits. No significant ERG or FA change was observed. The histology of retina remained unchanged. The pharmacokinetic profile of EPO in ocular compartments was summarized as follows. The half-life times of EPO in vitreous, aqueous and serum were 2.84, 3.24 and 2.12 d, respectively; and Cmax were 4615.75, 294.31 and 1.60 U/L, respectively. EPO concentrations in the retina of the injected eye peaked at 1.36 U/g protein at 6 h following injection, with the half-life observed to be 3.42 d.

CONCLUSIONS

IVit of EPO in a wide range is well tolerated and safe for rabbit eyes. At doses up to 10-fold higher than therapeutic levels, EPO has a pharmacokinetic profile with faster clearance, which is favorable for episodic IVit.

Pharmacokinetic and pharmacodynamic modeling of recombinant human erythropoietin after intravenous and subcutaneous administration in rats

The pharmacokinetics (PK) and pharmacodynamics (PD) of recombinant human erythropoietin (rHuEPO) were studied in rats after single i.v. and s.c. administration at three dose levels (450, 1350, and 4050 IU/kg). The plasma concentrations of rHuEPO and its erythropoietic effects including reticulocyte (RET), red blood cell (RBC), and hemoglobin (Hb) levels were determined. A two-compartment model with dual input rate and nonlinear disposition was used to characterize the PK of rHuEPO. The catenary indirect response model with several compartments reflecting the bone marrow and circulating erythropoietic cells was applied. The s.c. doses exhibited slow absorption (T(max) = 12 h) and incomplete bioavailability (F = 0.59). In placebo groups, RBC and Hb values gradually increased over time with growth of the rats, and the changes in the baselines monitored from 8 to 32 weeks of age were described by a nonlinear growth function. All doses resulted in dose-dependent increases in RET counts followed by an immediate decline below the baseline at around 6 days and returned to the predose level in 21-24 days after dosing. A subsequent steady increase of RBC and Hb levels followed and reached peaks at 6 days. A tolerance phenomenon observed at all dose levels was modeled by a negative feedback inhibition with the relative change in Hb level. The PK/PD model well described the erythropoietic effects of rHuEPO as well as tolerance, thereby yielding important PD parameters (S(max) = 1.87 and SC(50) = 65.37 mIU/ml) and mean lifespans of major erythropoietic cell populations in rats.

An Extended Terminal Half-Life for Darbepoetin Alfa

BACKGROUND AND OBJECTIVE

Anaemia is a major and persistent manifestation of chronic kidney disease (CKD) caused by the deficient production of erythropoietin in the kidneys, the prevalence of which is proportional to the deterioration in kidney function. Darbepoetin alfa, an erythropoiesis-stimulating protein, exhibits a lower clearance and longer terminal half-life in serum than recombinant human erythropoietin, thereby allowing for a reduced dosing frequency. A recent study in patients with CKD, using a 4-week sampling period, suggested that the terminal half-life of darbepoetin alfa in serum is longer than that reported in previous studies, which were based on a 1-week sampling period. This study was conducted to characterise the pharmacokinetic profile of a single subcutaneous dose of darbepoetin alfa 1 microg/kg in patients with CKD, using a sampling duration of 4 weeks, which was hypothesised to allow better characterisation of the terminal half-life in serum.

METHODS

Twenty patients with CKD not on dialysis, with a calculated glomerular filtration rate of 20-60 mL/min and who had not been treated with erythropoietic agents in the previous 12 weeks, were enrolled into this single-dose, open-label study. Patients received a single subcutaneous dose of darbepoetin alfa (Aranesp) 1 microg/kg on day 1, and blood samples were collected for pharmacokinetic analyses predose, 6 and 12 hours postdose and up to 28 days postdose. Seroreactivity sampling and further safety laboratory tests (clinical chemistry and urinalysis) were also performed. Patients were assessed for adverse events at each study visit. The primary endpoint was characterisation of the terminal half-life following a single subcutaneous dose of darbepoetin alfa 1 microg/kg.

RESULTS

The mean terminal half-life in serum of darbepoetin alfa was determined to be 69.6 hours. Peak serum concentrations were reached in a median time of 36 hours postdose, and a mean apparent clearance of 3.51 mL/h/kg was comparable to that observed previously in this patient population.

CONCLUSION

Based on an extended sampling schedule of 4 weeks, the terminal half-life of darbepoetin alfa was approximately 70 hours. This is longer than the 48.8 hours reported previously in patients with CKD on dialysis. These data suggest that the pharmacokinetic properties of darbepoetin alfa make this erythropoietic agent well suited to an extended dosing regimen.

Randomized cross-over comparison of intravenous and subcutaneous darbepoetin dosing efficiency in haemodialysis patients

BACKGROUND

Studies have consistently shown the superior dosing efficiency of subcutaneous (s.c.) compared to intravenous (i.v.) erythropoietin (r-HuEPO). Unlike r-HuEPO, data from pivotal darbepoetin trials support s.c. and i.v. dosing equivalence, however, no blinded cross-over randomized studies of s.c. and i.v. dose efficiency or intra-patient variability in response have been published.

METHODS

During this 12-month study, 53 haemodialysis patients were randomized to s.c. or i.v. darbepoetin for a 6-month period and then switched to the alternative route for a second 6-month period. Darbepoetin dose was titrated during the first 4-months of each period to achieve a stable haemoglobin during the final 2-month observation period of each arm.

RESULTS

Twenty-four patients were included in analysis. No significant difference between s.c. and i.v. administration was observed for any measured parameter. Patients achieved a non-significantly higher haemoglobin (123.6 +/- 3.76 vs 120.9 +/- 4.42 g/L, P = 0.11) from a non-significantly lower darbepoetin dose (40.8 +/- 10.7 vs 42.5 +/- 11.0 mcg/week, P = 0.23) with i.v. administration. The population-based weight normalized s.c./i.v. dose ratio was 1.04 (0.97-1.11). Despite no significant overall difference, some patients experienced changes in individual dose efficiency response. Three of 24 patients recorded a greater than 30% change, four of 24 recorded between a 20 and 30% change, and five of 24 patients recorded between a 10 and 20% change relative to i.v. dose efficiency.

CONCLUSIONS

This study further supports s.c. and i.v. dosing equality and that overall the more convenient i.v. route can be used with equal dosing efficiency. However, patients switching routes of administration should be monitored due to the wide range in individual response.

Lymphatic Absorption Is the Primary Contributor to the Systemic Availability of Epoetin Alfa following Subcutaneous Administration to Sheep

The contribution of the lymphatics to the absorption and systemic availability of recombinant human epoetin alfa (rHuEPO) following s.c. injection was examined using a cannulated sheep model. Parallel studies were conducted in sheep where a single bolus dose was administered either by i.v. (10, 100, or 1000 IU/kg) or s.c. (400 IU/kg) injection. The first s.c. group served as a control for the calculation of absolute bioavailability. In the second group, the efferent popliteal lymphatic duct was cannulated and peripheral lymph draining the injection site was continuously collected. In the third group, the thoracic duct was cannulated to allow collection of central lymph just prior to entry into the systemic circulation. Blood was periodically sampled from all animals, and concentrations in serum and lymph were determined by enzyme-linked immunosorbent assay. The cumulative amount of rHuEPO recovered in peripheral and central lymph was 83.9 +/- 6.6% and 75.3 +/- 3.9% of the administered dose, respectively, indicating almost complete absorption from the s.c. injection site and minimal clearance during transit through the lymphatic system. After i.v. administration, the systemic clearance of rHuEPO decreased with increasing dose, reflecting capacity-limited elimination kinetics. A pharmacokinetic model was developed to simultaneously fit experimental data for all treatment groups and estimate bioavailability. The direct measurement of >75% of the dose in peripheral and central lymph independently verifies the calculated bioavailability of 87% and demonstrates the major role of the lymphatic route in the overall s.c. bioavailability of rHuEPO after s.c. administration with this animal model.

An overview of the pharmacokinetic disposition of darbepoetin alfa

Darbepoetin alfa is a new erythropoiesis-stimulating protein that has five carbohydrate chains compared with three in recombinant human erythropoietin (r-HuEPO, epoetin alfa). Owing to its increased carbohydrate content, the terminal half-life of darbepoetin alfa is 2-3-fold greater than that of r-HuEPO in patients with chronic kidney disease or cancer. This pharmacokinetic property may allow for less frequent administration of darbepoetin alfa compared with r-HuEPO. Although several regimens are still being tested, a predictable increase was observed in serum concentrations of darbepoetin alfa and no clinically relevant accumulation was seen with once-weekly administration for up to 48 weeks. Preliminary data in patients with cancer suggest that concurrent chemotherapy may influence the pharmacokinetics of darbepoetin alfa. Therefore, the timing of dosing relative to chemotherapy may be important. Darbepoetin alfa, through its potential for less frequent dosing, offers a more convenient treatment option than r-HuEPO for patients with anemia secondary to cancer or kidney disease.

Meta-analysis of subcutaneous versus intravenous epoetin in maintenance treatment of anemia in hemodialysis patients

BACKGROUND

Clinical and pharmacokinetic studies have shown that target hemoglobin or hematocrit levels can be maintained using a reduced recombinant human erythropoietin (epoetin) dosage by switching from intravenous (IV) to subcutaneous (SC) administration.

METHODS

We conducted a meta-analysis of comparative studies of epoetin administered IV versus SC to assess the relative costs of these administration routes. Twenty-seven prospective clinical studies involving 916 patients were included in the analysis. The average difference between IV and SC doses of epoetin and average difference in drug costs between administration routes were determined.

RESULTS

The average reduction in dose in patients treated with SC versus IV epoetin was 48 IU/kg/wk (P < 0.001), representing an average annual cost savings with SC administration of US $1,761 +/- $1,080 (SD) per patient. The difference between SC and IV doses was similar in both parallel- and crossover-design studies. A retrospective US survey showed a dose reduction of 26 IU/kg/wk (P < 0.001) with SC administration, translating to an annual savings of $946 per patient.

CONCLUSION

This study indicates that the cost of epoetin is reduced substantially when administered SC in comparison to IV. Recommendations of current US and European guidelines, which encourage the use of SC administration, not only have a sound rationale in terms of efficacy and safety, but also have a sound economic basis.

Darbepoetin alfa: a new therapeutic agent for renal anemia

Darbepoetin alfa is a super-sialylated analog of human erythropoietin that has a longer circulating half-life in vivo compared to both native and recombinant hormone. It has the same mechanism of action as erythropoietin, stimulating the same surface membrane receptor and triggering the same intracellular chain of events. An extra two N-linked carbohydrate chains, however, gives darbepoetin alfa greater metabolic stability in vivo, and its terminal half-life after intravenous administration is approximately three times longer than for intravenous erythropoietin. This in turn allows injections of the drug to be given less frequently, and studies have shown that once-weekly and once-every-other-week dosing can maintain the hemoglobin concentration in patients with renal anemia. The recommended starting dose for darbepoetin alfa is 0.45 microg/kg once weekly for both IV and SC administration, with subsequent titration based on the hemoglobin concentration. The adverse event profile is very similar to that seen with rHuEPO, and no antibodies have been detected in several thousand patients exposed to the drug, some of whom have been treated for up to five years now. Following a clinical research program that began in November 1996, darbepoetin alfa was finally approved by the European Commission in June 201, and by the FDA in September 201.

Novel erythropoiesis stimulating protein for managing the anemia of chronic kidney disease

Since its introduction, recombinant human erythropoietin (rHuEPO) has become the standard of care for renal anemia. Because of its relatively short half-life, however, it generally is administered two to three times per week. Darbepoetin alfa (novel erythropoiesis stimulating protein [NESP]) is a longer acting erythropoietic agent that allows less frequent dosing to treat anemia. Decreased dosing frequency should result in enhanced patient compliance and convenience and minimize the burden of frequent administration on staff. NESP is biochemically distinct from rHuEPO, having five N-linked carbohydrate chains (two more than rHuEPO). In animal studies, NESP had a half-life approximately three times longer than rHuEPO and raised hemoglobin effectively when administered less frequently than rHuEPO. NESP has been evaluated in clinical trials of dialysis and chronic kidney disease patients. Pharmacokinetic data confirmed that patients with anemia required less frequent dosing with NESP than rHuEPO. After intravenous administration, the mean elimination half-life of NESP was 25.3 hours versus 8.5 hours for rHuEPO. In patients who are rHuEPO-naive and in patients previously managed with rHuEPO, NESP is as effective as rHuEPO for maintaining hemoglobin concentration when administered intravenously or subcutaneously at a reduced frequency of once weekly or once every other week. NESP is well tolerated and has a safety profile comparable to that of rHuEPO. There have been no reports of antibody formation associated with NESP. NESP is an important new tool for physicians to use in the treatment of anemia of chronic kidney disease.

Pharmacokinetics of novel erythropoiesis stimulating protein compared with epoetin alfa in dialysis patients

Novel erythropoiesis stimulating protein (NESP) is a hyperglycosylated analogue of recombinant human erythropoietin (Epoetin) which has an increased terminal half-life in animal models. The aim of this study was to extend these observations to humans. Using a double-blind, randomized, cross-over design, the single-dose pharmacokinetics of Epoetin alfa (100 U/kg) and an equivalent peptide mass of NESP were compared following intravenous bolus in 11 stable peritoneal dialysis patients. This was followed by an open-label study to determine the single-dose pharmacokinetics of an equivalent peptide mass of NESP by subcutaneous injection in six of these patients. The mean terminal half-life for intravenous NESP was threefold longer than for intravenous Epoetin (25.3 versus 8.5 h), a difference of 16.8 h (95% confidence interval, 9.4 to 24.2 h, P = 0.0008). The area under the serum concentration-time curve was significantly greater for NESP (291.0 +/- 7.6 ng x h per ml versus 131.9 +/- 8.3 ng x h per ml; mean +/- SEM; P < 0.0005), and clearance was significantly lower (1.6 +/- 0.3 ml/h per kg versus 4.0 +/- 0.3 ml/h per kg; mean +/- SEM; P < 0.0005). The volume of distribution was similar for NESP and Epoetin (52.4 +/- 2.0 ml/kg versus 48.7 +/-2.1 ml/kg; mean +/-SEM). The mean terminal half-life for subcutaneous NESP was 48.8 h. The peak concentration of subcutaneous NESP was approximately 10% of that following intravenous administration, and bioavailability was approximately 37% by the subcutaneous route. The longer half-life of NESP is likely to confer a clinical advantage over Epoetin by allowing less frequent dosing in patients treated for anemia.

Pharmacokinetics of intraperitoneal epoetin alfa in patients on peritoneal dialysis using an 8-hour "dry dwell" dosing technique

Pharmacokinetic studies of intraperitoneal (IP) epoetin alfa administered to continuous ambulatory peritoneal dialysis (CAPD) patients have shown low bioavailability, primarily attributable to the dilutional effect of coadministered dialysate. However, bioavailability is improved by instilling the dose into a dry peritoneum. The current study was designed to determine whether absorption after administration into a dry peritoneum is improved by extending the dry dosing period from 4 to 8 hours. The pharmacokinetics of a single 100-unit/kg IP epoetin alfa dose were studied in 8 noninfected CAPD patients. The dose was instilled into a dry peritoneum via the peritoneal catheter and allowed to dwell for 8 hours. CAPD was then resumed. Blood samples were collected for 96 hours after the dose. A 14-hour effluent dialysate sample was collected to determine epoetin alfa recovery. Enzyme immunoassay was used for epoetin alfa analysis of serum and effluent. Standard pharmacokinetic methods were employed for analysis of the serum concentration time data. The extent of epoetin alfa absorption was significantly greater than previously reported for a 4-hour dry dwell. The mean (+/-SD) dose-normalized area-under-the-curve (nlAUC(0-infinity)) using the 8-hour dry dwell dosing technique was 6,331 +/- 2,536 mIU. h/mL. This is significantly greater than the value of 2,589 +/- 1,450 mIU. h/mL (two-sided P value = 0.002) from a previous study in which patients received the same 100-unit/kg dose using a 4-hour dry dwell. The absorption of epoetin alfa administered by the intraperitoneal route is improved by extending the time the dose resides in a dry peritoneum.

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

In children treated by continuous ambulatory peritoneal dialysis (CAPD) renal anaemia is preferably treated by intraperitoneal administration of erythropoietin, since subcutaneous administration is painful and frightening for the child. Pharmacokinetics of erythropoietin were studied in three groups of children treated by CAPD. In group subcutaneous (SC) (n = 5) erythropoietin was administered subcutaneously, whereas in group intraperitoneal 1 (IP1) (n = 8) and intraperitoneal 2 (IP2) (n = 8) erythropoietin was given intraperitoneally during a 12-h dwell. Group IP1 received erythropoietin in 20 ml/kg of dialysis fluid, while in group IP2 the hormone was added to only 50 ml of dialysate, irrespective of body weight. The median area under the curve (AUC) was 4064 mU.h/ml (range 2647-24357) in group SC, 1698 (570-5514) in group IP1 and 3577 (1225-6555) in group IP2. In comparison to group SC the AUC was significantly lower in group IP1 (Wilcoxon: P = 0.02). The difference between group SC and group IP2 was not statistically significant.

CONCLUSION

In children on CAPD the resorption of erythropoietin after intraperitoneal administration, measured as AUC, is similar to subcutaneous administration, when erythropoietin is administered in 50 ml of dialysate. The dose needed to treat renal anaemia with erythropoietin administered intraperitoneally this way will have to be established in a therapeutic study.

Optimizing epoetin therapy in end-stage renal disease: the case for subcutaneous administration

The effectiveness of various recombinant human erythropoietin (epoetin) administration routes and dosage schedules in patients on dialysis was studied. The mean dose required to achieve and maintain a hematocrit level between 33% and 40% is 225 U/kg/wk when administered intravenously (i.v.) in three divided doses. A once-weekly i.v. schedule requires a dose of 429 U/kg/wk to maintain the same target hematocrit. In contrast, the required epoetin dose is reduced by an average of 25% to 50% when administered via the subcutaneous (SC) route. Analysis of data from 25 dialysis centers shows that SC epoetin administration resulted in higher normalized responses than i.v. administration. The hematocrit response in patients at these centers was proportional to the weekly dose, with a greater slope in those centers using predominantly SC as compared with i.v. dosing. Cost analysis indicates that the use of SC dosing two or three times weekly at an average total weekly dose of 120 U/kg is effective for the treatment of anemia in most patients on dialysis.

Pharmacokinetics of intraperitoneal, intravenous, and subcutaneous recombinant human erythropoietin in patients on continuous ambulatory peritoneal dialysis

The pharmacokinetics of recombinant human erythropoietin (Epo) were compared after mean single 99.1 U/kg intraperitoneal (IP), intravenous (i.v.), and subcutaneous (SC) doses in eight noninfected patients on peritoneal dialysis in a randomized, three-way, cross-over fashion. Continuous ambulatory peritoneal dialysis was performed in all patients on the days of the study. The IP dose was instilled into an empty peritoneum; total dwell time was 10 hours (4 hours dry, 6 hours with 2 L of peritoneal dialysis fluid). Blood samples were collected for 96 hours following IP and SC Epo, and for 72 hours following i.v. Epo. For the IP dose, a 10-hour effluent dialysate sample was collected to determine Epo recovery. Enzyme immunoassay was used for Epo analysis. The mean apparent volume of distribution was 0.05 L/kg, equivalent to 4.5% of total body weight; the mean total body clearance was 0.08 mL/min/kg. All eight patients exhibited multiexponential decay in serum Epo concentrations following i.v. Epo. Absorption of IP Epo was significantly greater than previous reports, presumably due to its administration into a dry peritoneum. The maximum concentrations following the IP and SC doses were nearly identical, but amounted to only 5% of the maximum concentrations for the i.v. dose. Subcutaneous Epo took nearly twice as long as IP Epo to achieve peak serum concentrations (17.1 +/- 5.0 hours v 9.4 +/- 1.9 hours). Compared with the IP route, the SC dose achieved a higher area under the serum concentration time curve from time 0 to 96 hours (AUC0-96; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Intraperitoneal production of erythropoietin with continuous ambulatory peritoneal dialysis

Higher hematocrit and serum erythropoietin (EPO) levels have previously been shown in end-stage renal disease patients treated with continuous ambulatory peritoneal dialysis (CAPD) compared with hemodialysis. We investigated whether EPO was produced intraperitoneally in CAPD patients. EPO concentration was 3.5 +/- 0.3 mU/ml by radioimmunoassay in 26 samples of peritoneal dialysis effluent obtained from 15 CAPD patients. EPO was not detectable in the fresh unused dialysate. No correlation was observed between EPO levels in the serum and dialysis effluent. Peritoneal macrophages were isolated from the dialysis effluent of 9 CAPD patients after an overnight dwell. The culture supernatant obtained after 24 h of in vitro culture of a million cells yielded EPO of 3.5 +/- 0.3 mU/ml. Our study demonstrated that peritoneal macrophages from CAPD patients produce EPO on in vitro stimulation, and EPO is present in the dialysis effluent of CAPD patients.

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

The single-dose pharmacokinetics of recombinant human erythropoietin (rHuEPO) given SC was investigated in 20 patients aged 7-20 years at different stages of chronic renal failure. In a pilot study we confirmed the lower bioavailability of the drug in 2 children when given SC compared with the IV route (24% and 43%, respectively). Following administration of 4,000 units/m2, rHuEPO SC effective serum erythropoietin concentrations increased from a mean baseline level (+/- SD) of 23 +/- 13 units/l to a mean peak concentration of 265 +/- 123 units/l, which was reached after 14.3 +/- 9.4 h, followed by a slow decline until baseline values were attained at 72 h. Mean residence time was 30 +/- 9 h and mean elimination half-time 14.3 +/- 7 h. The single-dose kinetics of SC rHuEPO in children with different degrees of renal failure are comparable to those in adult patients. Possibly, the higher efficacy of SC rHuEPO in patients with renal anaemia compared with IV rHuEPO is related to its prolonged action.

Effects of azathioprine on response of renal anaemia to subcutaneous recombinant human erythropoietin

AIMS

To determine the effect of concomitant azathioprine treatment on the response of patients with renal failure to treatment with subcutaneous recombinant human erythropoietin (r-HuEPO).

METHODS

Two groups of patients with renal failure not receiving haemodialysis were studied. One comprised seven patients receiving erythropoietin alone, the second consisted of nine patients who were also treated with azathioprine. The haematological changes were monitored, and the functional erythropoietic response was studied by two different ferrokinetic models. One analysed the initial, the other the extended plasma iron clearance. Studies were performed before r-HuEPO treatment on all 16 patients, and repeated on 11 of these when the target haemoglobin (10-11 g/dl) was achieved and stabilised. Total erythropoiesis was determined using both techniques. Analysis of the extended plasma iron clearance also permitted calculation of both effective and ineffective erythroid activity.

RESULTS

The haematological response to r-HuEPO was the same for both patient groups. Measurement of total erythropoiesis by both ferrokinetic methods showed good correlation. For those receiving long term azathioprine, the percentage ineffective erythropoiesis was high compared with that of the other patients, and remained so for as long as they continued with azathioprine. For those uncomplicated by azathioprine treatment, r-HuEPO increased levels of both effective and ineffective erythropoiesis by the same degree. A substantial reduction in ineffective erythropoiesis was shown only by those patients who either discontinued or reduced their azathioprine once they started r-HuEPO treatment.

CONCLUSIONS

Azathioprine increases ineffective erythropoiesis. In this study, the r-HuEPO dose was sufficient to overcome this effect and promoted effective erythropoiesis so that the anaemia lessened. Measurement of total erythropoiesis provided limited information on the functional changes involved, differentiation of effective from ineffective erythropoiesis being necessary to define the changes after azathioprine reduction or withdrawal.

Intraperitoneal administration of recombinant human erythropoietin in children on continuous ambulatory peritoneal dialysis

In 16 children treated by continuous ambulatory peritoneal dialysis (CAPD) recombinant human erythropoietin was administered intraperitoneally for the treatment of renal anaemia. The mean treatment period was 8.3 months. Mean haemoglobin values increased from 4.9 mmol/l at start of therapy to 6.2 after 6 months. While 11 out of 16 children needed a total of 22 transfusions during the 6 months prior to therapy, no transfusions were needed after initiation of therapy. Patients started with a dose of 300 units/kg per week. After 6 months of therapy, the mean dose was 370 and after 12 months 279 units/kg per week. No major side-effects were observed. The incidence of peritonitis was not increased. We conclude that intraperitoneal administration of erythropoietin is effective in the treatment of renal anaemia in children treated by CAPD.

Weekly subcutaneous recombinant human erythropoietin corrects anemia of progressive renal failure

PURPOSE

The purpose of this study was to analyze data retrospectively from our use of weekly subcutaneous recombinant human erythropoietin (rHuEPO) in predialysis and peritoneal dialysis patients with anemia.

PATIENTS AND METHODS

All anemic patients with progressive renal failure (12 predialysis and seven home peritoneal dialysis) in whom subcutaneous rHuEPO therapy was begun at, or was reduced to, a weekly dose were studied retrospectively. Patients were not selected for, nor excluded from, these observations for any other reason. Hematocrit and endogenous creatinine clearance were monitored regularly, and no other new treatment for anemia was given except oral iron. Iron-deficiency anemia was considered improbable because of normal red blood cell mean corpuscular volume. Unfortunately, iron parameters were not monitored.

RESULTS

The hematocrit increased 4 to 9 percentage points in 4 to 13 weeks in all but two patients who were initially treated with weekly doses, and a hematocrit of 31% was achieved in these patients within 6 to 12 weeks. The mean effective dose to accomplish this was 150 U/kg. All but three patients could be maintained on weekly doses at a hematocrit of 31% or higher. The mean effective dose was 75 U/kg.

CONCLUSION

It is concluded that subcutaneous rHuEPO administered weekly can correct the anemia of predialysis and peritoneal dialysis patients. Weekly dosing is more convenient for patients and may be less costly for Medicare providers.

Low-dose subcutaneous erythropoietin in continuous ambulatory peritoneal dialysis

We evaluated changes in hematocrit in patients on continuous ambulatory peritoneal dialysis (CAPD) before and after the administration of erythropoietin (EPO). Thirty-five patients were evaluated at the beginning of treatment with CAPD and after an average of 3.5 years on CAPD; mean hematocrit (Hct) rose from 25.4 +/- 5.4% to 28.1 +/- 6.7% (P less than 0.001). In the period before EPO administration 11 patients required a total of 44 transfusions (one patient needed 23 transfusions). Fifteen patients were started on subcutaneous erythropoietin 3,000 units 3 times a week and were followed for a mean period of 6.3 months. Hct rose from 23.8 +/- 1.8% to 25.2 +/- 2.4% (P less than 0.01) within the first 2 weeks and up to 27.5 +/- 3.7% (P less than 0.01) in the fourth week. By the eighth week the target Hct (30 to 35%) was reached. During the next 5 months the EPO doses were adjusted to each patient's needs ranging between 2,000 U per week to 4,000 U 3 times per week. Mild hypertension was the only side effect seen in some of the patients. In conclusion low dose subcutaneous EPO is effective in managing the anemia of patients on CAPD with only minor side effects.

The use of erythropoietin in renal failure

The treatment of renal anaemia by recombinant human erythropoietin (EPO) is now well established. Several studies have examined the pharmacokinetics and efficacy of the drug given intravenously, intraperitoneally and subcutaneously and there is increasing evidence that the subcutaneous route has several advantages including the requirement for a lower dose. It is also important to stress the need for careful determination of baseline iron status of all patients before commencing EPO therapy. In the long term the extremely high iron stores of transfusion dependent patients will disappear. In the short term, however, the majority of the patients whose serum ferritin is less than 100 micrograms/l will require iron supplementation to allow an appropriate haemoglobin response. Alternatively, a fall in transferrin saturation to less than 20% is certainly an indication for iron supplementation and if oral iron therapy is not adequate then intravenous preparations may have to be considered. Although the anaemia of renal failure can be fully corrected by EPO, partial correction may be sufficient to reverse the problems of reduced exercise capacity, myocardial ischaemia and cardiomegaly which are frequently associated with end-stage renal disease. Partial correction will also result in a lesser rise in whole blood viscosity and, in turn, possibly reduce hypertension, thrombosis and increased peripheral resistance and thus lessen the side effects of EPO therapy.

Treating renal anaemia with recombinant human erythropoietin: practical guidelines and a clinical algorithm

Treatment with erythropoietin is highly effective and beneficial if given with care. In view of its cost, however, it is essential to exclude and treat other causes of anaemia before considering using this hormone. After treatment is started the important points for success are regular review of iron availability state combined with a slow correction of the anaemia. Failure of response requires a thorough search for a possible cause, which should be corrected before considering an increased dose of the hormone. Regular monitoring for potential complications, particularly a rise in blood pressure, is required.