Short-term small-dose intravenous iron trial to detect functional iron deficiency in dialysis patients

Iron Treatment Strategies in Dialysis-Dependent CKD

Iron deficiency is common in patients on chronic dialysis, and most require iron-replacement therapy. In addition to absolute iron deficiency, many patients have functional iron deficiency as shown by a suboptimal response to the use of erythropoietin-stimulating agents. Both absolute and functional iron-deficiency anemia have been shown to respond to intravenous (IV) iron replacement. Although parenteral iron is an efficacious method and superior to standard doses of oral iron in patients on hemodialysis, there are ongoing safety concerns about repeated exposure potentially enhancing infection risk and cardiovascular disease. Each IV iron product is composed of an iron core with a carbohydrate shell. The avidity of iron binding and the type of carbohydrate shell play roles in the safe maximal dose and the frequency and severity of acute infusion reactions. All IV iron products are taken up into the reticuloendothelial system where the shell is metabolized and the iron is stored within tissue ferritin or exported to circulating transferrin. IV iron can be given as large intermittent doses (loading therapy) or in smaller doses at frequent intervals (maintenance dosing regimen). Limited trial data and observational data suggest that a maintenance dosing regimen is more efficacious and possibly safer than loading therapy. There is no consensus regarding the preferred method of iron repletion in patients on peritoneal dialysis, although small studies comparing oral and parenteral iron regimens in these patients have shown the latter to be more efficacious. Use of IV iron in virtually all hemodialysis and many peritoneal dialysis patients remains the standard of care.

Update on intravenous iron choices

PURPOSE OF REVIEW

Iron deficiency is a major factor in the prevalence and severity of anemia in patients with chronic kidney disease (CKD). We review the pathophysiology impairing normal intestinal iron absorption in CKD and compare the characteristics of newer intravenous (i.v.) iron agents to the longstanding i.v. iron products in the market.

RECENT FINDINGS

The newer iron products, ferumoxytol, ferric carboxymaltose, and iron isomaltoside, more avidly bind iron, minimizing the release of labile iron during infusions, thus permitting large dose infusions. These irons also have more complex carbohydrate shells than their predecessors, which may also diminish reactions. Newer agents can be routinely administered at higher single doses, in as little as 15 min, with an acceptable safety profile.

SUMMARY

Newer i.v. iron products permit the rapid, and sometimes complete, repletion of iron-deficient patients with a single dose. However, further studies examining the long-term risks and benefits of i.v. iron repletion are needed.

Diagnosis of iron deficiency in patients undergoing hemodialysis

To diagnose iron deficiency in patients undergoing hemodialysis, the percentage of hypochromic RBCs (with cellular hemoglobin concentration <280 g/L [HYPO%]) and mean reticulocyte hemoglobin content (CHret) provided by the Siemens ADVIA 120 and 2120 analyzers (Siemens Diagnostic Solutions, Tarrytown, NY) were proposed as alternatives to biochemical tests. Sysmex, with its XE-5000 analyzer (Sysmex, Kobe, Japan), also proposed the percentage of erythrocytes with cellular hemoglobin content lower than 17 pg (%Hypo-He) and equivalent of the mean reticulocyte hemoglobin content (Ret-He) with similar clinical applications. Our aim was to verify the clinical usefulness of the biochemical and cellular parameters as predictors of iron deficiency in patients undergoing long-term hemodialysis. We studied 69 patients undergoing hemodialysis 3 times weekly. The baseline values of serum ferritin and percentage of transferrin saturation were poor predictors of iron responsiveness. Better ability was demonstrated by reticulocyte indices (area under the curve [AUC], 0.74 for CHret and 0.72 for Ret-He; best cutoff values, 31.2 and 30.6 pg, respectively) and erythrocyte parameters (AUC, 0.72 for HYPO% and 0.68 for %Hypo-He; best cutoff values, 5.8 and 2.7, respectively). The newly proposed Ret-He and %Hypo-He can provide clinicians with information equivalent to CHret and HYPO%.

Effectiveness of oral and intravenous iron therapy in haemodialysis patients

Anaemia is a common and serious complication in patients with end-stage renal disease. Iron therapy is crucial in managing anaemia and maintenance of haemodialysis (HD) patients. This study investigated the efficacy of both oral and intravenous (i.v.) therapies, and the possible factors deleteriously affecting patient response to iron therapy. Forty patients on maintenance HD from a single institution were enrolled in this 6-month retrospective study. Group I (n = 20) received i.v. two ampoules of atofen (ferric chloride hexahydrate 193.6 mg) per week for a total of 6 weeks (total dosage, 960 mg). Group II (n = 20) received oral ferrous sulphate S.C. Tab (ferrous sulphate 324 mg) one pill three times daily (total dosage, 63,000 mg). Patients whose haematocrit (Hct) level increased at minimum 3% within the period were classified as responders. Iron i.v. ferric chloride (960 mg) was more effective than oral ferrous sulphate (63,000 mg) in correcting anaemia in HD patients with iron deficiency. In group I, serum triglyceride (TG) levels were significantly lower in patients responding to i.v. iron therapy than in patients with no response. In group II, serum high-sensitive C-reactive protein (hs-CRP) level was significantly lower in patients responding to oral iron therapy than patients with no response. The i.v. ferric chloride is more effective than oral ferrous sulphate in treating anaemia in HD patients with iron deficiency. Serum hs-CRP and TG levels may be parameters for predicting hyporesponsiveness to oral and i.v. iron therapies, respectively.

Predictors of the response to treatment in anemic hemodialysis patients with high serum ferritin and low transferrin saturation

Treating hemodialysis patients to combat anemia corrects hemoglobin but exacerbates iron deficiency by utilizing iron stores. Patients needing iron should receive this by intravenous (i.v.) means. The Dialysis patients' Response to IV iron with Elevated ferritin (DRIVE) trial investigated the role of i.v. iron in anemic patients with high ferritin, low transferrin saturation, and adequate epoetin doses. We examined whether baseline iron and inflammation markers predict the response of hemoglobin to treatment. Patients (134) were randomized to no added iron or to i.v. ferric gluconate for eight consecutive hemodialysis sessions spanning 6 weeks with epoetin increased by 25% in both groups. The patients started with hemoglobin less than or equal to 11 g/dl, ferritin between 500 and 1200 ng/ml, and transferrin saturation of less than 25%. Significantly, patients with a reticulocyte hemoglobin content greater than or equal to 31.2 pg were over five times more likely to achieve a clinically significant increase in hemoglobin of greater than 2 g/dl. Lower reticulocyte hemoglobin contents did not preclude a response to i.v. iron. Significantly higher transferrin saturation or lower C-reactive protein but not ferritin or soluble transferrin receptor levels predicted a greater response; however their influence was not clinically significant in either group. We conclude that none of the studied markers is a good predictor of response to anemia treatment in this patient sub-population.

Ferric gluconate is highly efficacious in anemic hemodialysis patients with high serum ferritin and low transferrin saturation: results of the Dialysis Patients' Response to IV Iron with Elevated Ferritin (DRIVE) Study

Few data exist to guide treatment of anemic hemodialysis patients with high ferritin and low transferrin saturation (TSAT). The Dialysis Patients' Response to IV Iron with Elevated Ferritin (DRIVE) trial was designed to evaluate the efficacy of intravenous ferric gluconate in such patients. Inclusion criteria were hemoglobin <or=11 g/dl, ferritin 500 to 1200 ng/ml, TSAT <or=25%, and epoetin dosage >or=225 IU/kg per wk or >or=22,500 IU/wk. Patients with known infections or recent significant blood loss were excluded. Participants (n=134) were randomly assigned to no iron (control) or to ferric gluconate 125 mg intravenously with eight consecutive hemodialysis sessions (intravenous iron). At randomization, epoetin was increased 25% in both groups; further dosage changes were prohibited. At 6 wk, hemoglobin increased significantly more (P=0.028) in the intravenous iron group (1.6 +/- 1.3 g/dl) than in the control group (1.1 +/- 1.4 g/dl). Hemoglobin response occurred faster (P=0.035) and more patients responded after intravenous iron than in the control group (P=0.041). Ferritin <or=800 or >800 ng/ml had no relationship to the magnitude or likelihood of responsiveness to intravenous iron relative to the control group. Similarly, the superiority of intravenous iron compared with no iron was similar whether baseline TSAT was above or below the study median of 19%. Ferritin decreased in control subjects (-174 +/- 225 ng/ml) and increased after intravenous iron (173 +/- 272 ng/ml; P<0.001). Intravenous iron resulted in a greater increase in TSAT than in control subjects (7.5 +/- 7.4 versus 1.8 +/- 5.2%; P<0.001). Reticulocyte hemoglobin content fell only in control subjects, suggesting worsening iron deficiency. Administration of ferric gluconate (125 mg for eight treatments) is superior to no iron therapy in anemic dialysis patients receiving adequate epoetin dosages and have a ferritin 500 to 1200 ng/ml and TSAT <or=25%.

Managing erythropoietin hyporesponsiveness

The anemia of chronic kidney disease is associated with cardiovascular disease, decreased quality of life, and mortality. The introduction of recombinant human erythropoietin (rHuEPO) has transformed the management of this condition. However, a significant proportion of patients fail to respond to even high doses of rHuEPO. Several factors have been implicated in the hyporesponsiveness to rHuEPO. Iron deficiency, whether absolute or functional, is considered the most important, and maintenance of adequate iron stores reduces rHuEPO requirements among patients on hemodialysis. However, traditional indices of iron that are currently utilized may not reflect iron stores accurately, and there is also increasing concern regarding the potential long-term toxicity of parenteral iron therapy. Infection and inflammation also influence the response to rHuEPO, both by disruption of iron metabolism and by eliciting the release of cytokines that inhibit erythropoiesis. Oxidative stress may contribute to rHuEPO hyporesponsiveness directly by promoting lipid peroxidation in cell membranes, leading to increased erythrocyte fragility and reduced life span and also through its strong association with inflammation. Severe hyperparathyroidism can lead to a reduced number of erythroid progenitor cells. Inadequate dialysis dose, aluminum overload, nutritional factors such as deficiencies of carnitine, vitamin B12, folic acid, and vitamin C can also reduce the efficacy of rHuEPO therapy. Hyporesponsiveness to rHuEPO presents a challenge to both diagnosis and management in an era where optimizing response to rHuEPO is critical both in limiting the burgeoning costs of anemia management and improving clinical outcomes in the dialysis population.

Weekly low-dose treatment with intravenous iron sucrose maintains iron status and decreases epoetin requirement in iron-replete haemodialysis patients

BACKGROUND

Haemodialysis patients need sustained treatment with intravenous iron because iron deficiency limits the efficacy of recombinant human epoetin therapy in these patients. However, the optimal intravenous iron maintenance dose has not been established yet.

METHODS

We performed a prospective multicentre clinical trial in iron-replete haemodialysis patients to evaluate the efficacy of weekly low-dose (50 mg) intravenous iron sucrose administration for 6 months to maintain the iron status, and to examine the effect on epoetin dosage needed to maintain stable haemoglobin values in these patients. Fifty patients were enrolled in this prospective, open-label, single arm, phase IV study.

RESULTS

Forty-two patients (84%) completed the study. After 6 months of intravenous iron sucrose treatment, the mean ferritin value showed a tendency to increase slightly from 405 +/- 159 at baseline to 490 +/- 275 microg/l at the end of the study, but iron, transferrin levels and transferrin saturation did not change. The haemoglobin level remained stable (12 +/- 1.1 at baseline and 12.1 +/- 1.5 g/dl at the end of the study). The mean dose of darbepoetin alfa could be reduced from 0.75 to 0.46 microg/kg/week; epoetin alfa was decreased from 101 to 74 IU/kg/week; and the mean dose of epoetin beta could be reduced from 148 to 131 IU/kg/week at the end of treatment.

CONCLUSIONS

A regular 50 mg weekly dosing schedule of iron sucrose maintains stable iron stores and haemoglobin levels in haemodialysed patients and allows considerable dose reductions for epoetins. Low-dose intravenous iron therapy may represent an optimal approach to treat the continuous loss of iron in dialysis patients.