Hypophosphatemia in children treated with ferric carboxymaltose

Intravenous iron therapy in pediatrics: who should get it and when is the right time?

Iron-deficiency anemia occurs most commonly in young children due to a low-iron diet and adolescent girls due to menstrual blood loss. However, children with gastrointestinal conditions such as intestinal failure, inflammatory bowel disease, celiac disease, and/or other chronic conditions, including chronic kidney disease and heart failure, also commonly have iron deficiency. Many patients with classic iron-deficiency anemia will improve with oral iron therapy. However, in children who have an incomplete response to oral iron, intravenous iron therapy is increasingly being used. Benefits of intravenous iron therapy include a rapid repletion of iron stores in addition to resolution of anemia, less gastrointestinal side effects, and relief for patients and families struggling with long-term iron supplementation. Indications for first-line therapy with intravenous iron in children with chronic conditions have also increased. Four intravenous iron formulations have approved indications in pediatrics, and many are increasingly used off-label in children as well. Here we discuss the indications and appropriate timing of intravenous iron therapy in children with a wide range of underlying etiologies.

Intravenous ferric carboxymaltose for the management of iron deficiency and iron deficiency anaemia in children and adolescents: a review

Iron deficiency is the primary cause of anaemia worldwide and is particularly common among children and adolescents. Intravenous (IV) iron therapy is recommended for paediatric patients with certain comorbidities or if oral iron treatment has been unsuccessful. IV ferric carboxymaltose (FCM) has recently been approved by the US Food and Drug Administration for use in children aged > 1 year. This narrative review provides an overview of the available publications on the efficacy and safety of IV FCM in children and adolescents. A literature search using PubMed and Embase yielded 153 publications; 33 contained clinical data or reports on clinical experience relating to IV FCM in subjects < 18 years of age and were included in the review. No prospective, randomised controlled studies on the topic were found. Most publications were retrospective studies or case reports and included patients with various underlying conditions or patients with inflammatory bowel disease. Efficacy data were included in 27/33 publications and improvements in anaemia, and/or iron status parameters were reported in 26 of them. Safety data were included in 25/33 publications and were in line with the adverse events described in the prescribing information.

CONCLUSION

The available publications indicate that IV FCM, a nanomedicine with a unique and distinctive therapeutic profile, is an effective and generally well-tolerated treatment for iron deficiency or iron deficiency anaemia in children and adolescents. Despite the wealth of retrospective evidence, prospective, randomised controlled trials in the paediatric setting are still necessary.

WHAT IS KNOWN

• Iron deficiency and iron deficiency anaemia are usually managed using oral iron therapy, but intravenous iron therapy is recommended for certain paediatric patients. • Intravenous ferric carboxymaltose (FCM) has recently been approved in the US for use in children aged > 1 year.

WHAT IS NEW

• Despite evidence that FCM is effective and generally well tolerated in children and adolescents, so far, only retrospective studies, non-randomised uncontrolled prospective studies, or case reports have been published in full. • There is a strong need for prospective, randomised controlled trials on FCM in the paediatric setting.

High-Dose Intravenous Iron with Either Ferric Carboxymaltose or Ferric Derisomaltose: A Benefit-Risk Assessment

The intravenous iron formulations ferric carboxymaltose (FCM) and ferric derisomaltose (FDI) offer the possibility of administering a large amount of iron in one infusion. This results in faster correction of anemia and the formulations being better tolerated than oral iron formulations. This triad of logistic advantages, improved patient convenience, and fast correction of anemia explains the fact that intravenous iron formulations nowadays are frequently prescribed worldwide in the treatment of iron deficiency anemia. However, these formulations may result in hypophosphatemia by inducing a strong increase in active fibroblast growth factor-23 (FGF-23), a hormone that stimulates renal phosphate excretion. This effect is much more pronounced with FCM than with FDI, and therefore the risk of developing hypophosphatemia is remarkably higher with FCM than with FDI. Repeated use of FCM may result in severe osteomalacia, which is characterized by bone pain, Looser zones (pseudofractures), and low-trauma fractures. Intravenous iron preparations are also associated with other adverse effects, of which hypersensitivity reactions are the most important and are usually the result of a non-allergic complement activation on nanoparticles of free labile iron-Complement Activation-Related Pseudo-Allergy (CARPA). The risk on these hypersensitivity reactions can be reduced by choosing a slow infusion rate. Severe hypersensitivity reactions were reported in < 1% of prospective trials and the incidence seems comparable between the two formulations. A practical guideline has been developed based on baseline serum phosphate concentrations and predisposing risk factors, derived from published cases and risk factor analyses from trials, in order to establish the safe use of these formulations.

Analysis of Transition from Intravenous Iron Sucrose to Ferric Carboxymaltose Infusions in Pediatric Intestinal Failure Patients

BACKGROUND

Iron supplementation is required for pediatric patients with intestinal failure (IF). There is a paucity of literature on optimal iron formulation and outcomes in this patient population that requires ongoing supplementation. The aim of this study was to assess outcomes in pediatric patients with IF receiving iron sucrose (IS) versus ferric carboxymaltose (FCM) iron infusions.

METHODS

This was a single-center observational cohort study of pediatric patients with IF requiring ongoing intravenous iron supplementation. Patients were transitioned from IS to FCM as iron therapy. Longitudinal linear mixed-effects models and generalized estimating equations were used to compare outcomes including hematologic, iron, and growth parameters for 12 months treatment duration on each iron formulation. Adverse effects were descriptively summarized.

RESULTS

Twenty-three patients were included. Sixteen received IS and later switched to FCM, 5 received IS only, and 2 received FCM only. Most patients' etiology of IF was short bowel syndrome (FCM: 81%, IS: 83%). No differences were seen over time for iron, hematologic, and growth metrics between IS and FCM. The median number of infusions over 12 months for those taking IS was 15 (IQR = 13 - 26) and 2 for FCM (IQR = 1 - 2). Asymptomatic hypophosphatemia was noted in both groups. Similar central line associated blood steam infection rates were noted.

CONCLUSIONS

IS and FCM infusions both maintained hematologic and iron parameters with no significant difference noted between the two types of iron though the number of FCM infusions was significantly less. No significant adverse effects were noted.

CLINICAL RELEVANCY STATEMENT

Pediatric patients with intestinal failure dependent on parenteral nutrition require ongoing iron supplementation. Though there are a variety of iron formulations available, there is a paucity of literature on how iron should be administered in this patient population. Practice varies widely among different institutions. In this study, pediatric patients with intestinal failure were transitioned from iron sucrose to ferric carboxymaltose infusions, and laboratory and clinical outcomes were compared. We found that patients had comparable hematologic and iron parameters with significantly fewer infusions needed in the ferric carboxymaltose group. No significant adverse effects were noted in either group. This article is protected by copyright. All rights reserved.

Safety of Ferric Carboxymaltose in Children: Report of a Case Series from Greece and Review of the Literature

BACKGROUND

Parenteral iron is generally considered safe in adults, and severe adverse events are extremely rare. Ferric carboxymaltose (FCM), a third-generation parenteral iron product, is not licensed for pediatric use.

OBJECTIVE

The aim of this study was to present our data on the safety of FCM in children with iron deficiency (ID) and/or iron deficiency anemia (IDA) and to investigate through a systematic literature review articles reporting on the safety of FCM use in children with ID/IDA.

PATIENTS AND METHODS

Safety data regarding children treated with FCM for ID/IDA from four pediatric departments in Greece over a 26-month period are presented. Additionally, a literature search was performed in PubMed, Scopus, and Google Scholar on December 4, 2021 for articles reporting on the use of FCM in children with ID/IDA. Review articles, guidelines, case reports/case series, and reports on the use of FCM for conditions other than ID/IDA were excluded. Identified articles were screened for all reported adverse events (AE) that were graded according to the Common Terminology Criteria for Adverse Events, version 5.0.

RESULTS

In our cohort, 37 children with ID/IDA received 41 FCM infusions. All infusions were tolerated well. In addition, 11 articles reporting 1231 infusions of FCM in 866 children were identified in the literature. Among them, 52 (6%) children developed AE that were graded as mild or moderate (grades I-III).

CONCLUSIONS

Our patient cohort and this literature review provide further evidence for the good safety profile of FCM in children, although well-designed prospective clinical trials with appropriate safety endpoints are still required.

Renal Phosphate Handling: Independent Effects of Circulating FGF23, PTH, and Calcium

Excess fibroblast growth factor 23 (FGF23), excess PTH, and an increase in extracellular calcium cause hypophosphatemia by lowering the maximum renal phosphate reabsorption threshold (TmP/GFR). We recently reported two cases of X-linked hypophosphatemia (XLH) with severe tertiary hyperparathyroidism who had normalization of TmP/GFR upon being rendered hypoparathyroid following total parathyroidectomy, despite marked excess in both C-terminal FGF23 (cFGF23) and intact FGF23 (iFGF23). We explored the effects of FGF23, PTH, and calcium on TmP/GFR in a cross-sectional study (n = 74) across a spectrum of clinical cases with abnormalities in TmP/GFR, PTH, and FGF23. This comprised three groups: FGF23-dependent hypophosphatemia (n = 27), hypoparathyroidism (HOPT; n = 17), and chronic kidney disease (n = 30). Measurements included TmP/GFR, cFGF23, PTH, ionized calcium, vitamin D metabolites, and bone turnover markers. The combined effect of cFGF23, PTH, and ionized calcium on TmP/GFR was modeled using hierarchical multiple regression and was probed by moderation analysis with PROCESS. Modeling analysis showed independent effects on TmP/GFR by cFGF23, PTH, and ionized calcium in conjunction with a weak but significant effect of the interaction term for PTH and FGF23; probing showed that the effect was most prominent during PTH deficiency. Teriparatide 20 μg daily was self-administered for 28 days by one case of X-linked hypophosphatemia with hypoparathyroidism (XLH-HOPT) to assess the response of TmP/GFR, cFGF23, iFGF23, nephrogenous cyclic adenosine monophosphate (NcAMP), vitamin D metabolites, and bone turnover markers. After 28 days, TmP/GFR was lowered from 1.10 mmol/L to 0.48 mmol/L; this was accompanied by increases in NcAMP, ionized calcium, and bone turnover markers. In conclusion, the effect of FGF23 excess on TmP/GFR is altered by PTH such that the effect is ameliorated by hypoparathyroidism and the effect is augmented by hyperparathyroidism. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.