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      Hypophosphatemia Associated with Intravenous Iron Therapies for Iron Deficiency Anemia: A Systematic Literature Review

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          Iron deficiency anemia (IDA) is a prevalent yet underdiagnosed condition with a significant impact on quality of life. Oral iron supplementation is often poorly tolerated or yields inadequate response, requiring the use of intravenous iron (IVI) in some patients. Administration of certain IVI preparations has been associated with decreases in serum phosphate levels and clinically significant hypophosphatemia, which has been reported to lead to adverse events including serious fatigue and osteomalacia.


          The purpose of this study was to systematically assess the prevalence, clinical consequences, and reporting of treatment-emergent hypophosphatemia within literature investigating IVI therapies marketed in the United States (US).


          A systematic literature review (SLR) was conducted using the PubMed database to identify publications reporting serum phosphate levels or rates of hypophosphatemia within adult IDA patient populations receiving current US-marketed IVIs.


          The SLR yielded 511 unique publications, with 40 records meeting the final inclusion criteria. Most studies did not report phosphate monitoring methodology or an explicit definition of hypophosphatemia. Hypophosphatemia rates ranged from 0.0% to 92.1% for ferric carboxymaltose (FCM), 0.0% to 40.0% for iron sucrose, 0.4% for ferumoxytol, and 0.0% for low-molecular-weight (LMW) iron dextran. Randomized controlled studies described hypophosphatemia as “asymptomatic” or did not report on other associated sequelae. Eleven case reports detailed treatment-emergent hypophosphatemia in patients treated with FCM. Patients with acute hypophosphatemia primarily developed severe fatigue; those with repeated FCM dosing developed chronic hypophosphatemia associated with osteomalacia and bone deformities.


          Studies analyzed in this SLR reported a range of hypophosphatemia rates, with the highest consistently seen in patients treated with FCM. Across the clinical literature, there appeared to be minimal standardization of phosphate monitoring and definitions of hypophosphatemia. Although multiple cases have documented serious clinical consequences of hypophosphatemia associated with certain IVIs, current trials neither consistently nor adequately assess the frequency and severity of treatment-emergent hypophosphatemia and may underestimate its prevalence.

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          Most cited references 57

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          Effects of iron deficiency anemia and its treatment on fibroblast growth factor 23 and phosphate homeostasis in women.

          Fibroblast growth factor 23 (FGF23) is an osteocyte-derived hormone that regulates phosphate and vitamin D homeostasis. Through unknown mechanisms, certain intravenous iron preparations induce acute, reversible increases in circulating FGF23 levels that lower serum phosphate in association with inappropriately low levels of calcitriol, similar to genetic diseases of primary FGF23 excess. In contrast, studies in wild-type mice suggest that iron deficiency stimulates fgf23 transcription but does not result in hypophosphatemia because FGF23 is cleaved within osteocytes by an unknown catabolic system. We tested the association of iron deficiency anemia with C-terminal FGF23 (cFGF23) and intact FGF23 (iFGF23) levels in 55 women with a history of heavy uterine bleeding, and assessed the longitudinal biochemical response over 35 days to equivalent doses of randomly-assigned, intravenous elemental iron in the form of ferric carboxymaltose (FCM) or iron dextran. Iron deficiency was associated with markedly elevated cFGF23 (807.8 ± 123.9 relative units [RU]/mL) but normal iFGF23 (28.5 ± 1.1 pg/mL) levels at baseline. Within 24 hours of iron administration, cFGF23 levels fell by approximately 80% in both groups. In contrast, iFGF23 transiently increased in the FCM group alone, and was followed by a transient, asymptomatic reduction in serum phosphate <2.0 mg/dL in 10 women in the FCM group compared to none in the iron dextran group. Reduced serum phosphate was accompanied by increased urinary fractional excretion of phosphate, decreased calcitriol levels, and increased parathyroid hormone levels. These findings suggest that iron deficiency increases cFGF23 levels, and that certain iron preparations temporarily increase iFGF23 levels. We propose that intravenous iron lowers cFGF23 in humans by reducing fgf23 transcription as it does in mice, whereas carbohydrate moieties in certain iron preparations may simultaneously inhibit FGF23 degradation in osteocytes leading to transient increases in iFGF23 and reduced serum phosphate. Copyright © 2013 American Society for Bone and Mineral Research.
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            Ferrous Sulfate Supplementation Causes Significant Gastrointestinal Side-Effects in Adults: A Systematic Review and Meta-Analysis

            Background The tolerability of oral iron supplementation for the treatment of iron deficiency anemia is disputed. Objective Our aim was to quantify the odds of GI side-effects in adults related to current gold standard oral iron therapy, namely ferrous sulfate. Methods Systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating GI side-effects that included ferrous sulfate and a comparator that was either placebo or intravenous (IV) iron. Random effects meta-analysis modelling was undertaken and study heterogeneity was summarised using I2 statistics. Results Forty three trials comprising 6831 adult participants were included. Twenty trials (n = 3168) had a placebo arm and twenty three trials (n = 3663) had an active comparator arm of IV iron. Ferrous sulfate supplementation significantly increased risk of GI side-effects versus placebo with an odds ratio (OR) of 2.32 [95% CI 1.74–3.08, p<0.0001, I2 = 53.6%] and versus IV iron with an OR of 3.05 [95% CI 2.07-4.48, p<0.0001, I2 = 41.6%]. Subgroup analysis in IBD patients showed a similar effect versus IV iron (OR = 3.14, 95% CI 1.34-7.36, p = 0.008, I2 = 0%). Likewise, subgroup analysis of pooled data from 7 RCTs in pregnant women (n = 1028) showed a statistically significant increased risk of GI side-effects for ferrous sulfate although there was marked heterogeneity in the data (OR = 3.33, 95% CI 1.19-9.28, p = 0.02, I2 = 66.1%). Meta-regression did not provide significant evidence of an association between the study OR and the iron dose. Conclusions Our meta-analysis confirms that ferrous sulfate is associated with a significant increase in gastrointestinal-specific side-effects but does not find a relationship with dose.
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              FERGIcor, a randomized controlled trial on ferric carboxymaltose for iron deficiency anemia in inflammatory bowel disease.

              Iron deficiency anemia (IDA) is common in chronic diseases and intravenous iron is an effective and recommended treatment. However, dose calculations and inconvenient administration may affect compliance and efficacy. We compared the efficacy and safety of a novel fixed-dose ferric carboxymaltose regimen (FCM) with individually calculated iron sucrose (IS) doses in patients with inflammatory bowel disease (IBD) and IDA. This randomized, controlled, open-label, multicenter study included 485 patients with IDA (ferritin <100 μg/L, hemoglobin [Hb] 7-12 g/dL [female] or 7-13 g/dL [male]) and mild-to-moderate or quiescent IBD at 88 hospitals and clinics in 14 countries. Patients received either FCM in a maximum of 3 infusions of 1000 or 500 mg iron, or Ganzoni-calculated IS dosages in up to 11 infusions of 200 mg iron. Primary end point was Hb response (Hb increase ≥ 2 g/dL); secondary end points included anemia resolution and iron status normalization by week 12. The results of 240 FCM-treated and 235 IS-treated patients were analyzed. More patients with FCM than IS achieved Hb response (150 [65.8%] vs 118 [53.6%]; 12.2% difference, P = .004) or Hb normalization (166 [72.8%] vs 136 [61.8%]; 11.0% difference, P = .015). Both treatments improved quality of life scores by week 12. Study drugs were well tolerated and drug-related adverse events were in line with drug-specific clinical experience. Deviations from scheduled total iron dosages were more frequent in the IS group. The simpler FCM-based dosing regimen showed better efficacy and compliance, as well as a good safety profile, compared with the Ganzoni-calculated IS dose regimen. Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.

                Author and article information

                Ther Clin Risk Manag
                Ther Clin Risk Manag
                Therapeutics and Clinical Risk Management
                08 April 2020
                : 16
                : 245-259
                [1 ]UCLA School of Medicine , Los Angeles, CA, USA
                [2 ]AMAG Pharmaceuticals, Inc ., Waltham, MA, USA
                [3 ]Trinity LifeSciences , Waltham, MA, USA
                Author notes
                Correspondence: Naomi V Dahl AMAG Pharmaceuticals, Inc ., 1100 Winter Street, Waltham, MA02451, USATel +1 617-498-7650 Email ndahl@amagpharma.com
                © 2020 Glaspy et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                Page count
                Figures: 4, Tables: 1, References: 63, Pages: 15
                Funded by: AMAG Pharmaceuticals, Inc
                Funded by: Trinity LifeSciences, funded by AMAG Pharmaceuticals, Inc
                This study was sponsored by AMAG Pharmaceuticals, Inc. Editorial support in the preparation of this manuscript was provided by Trinity LifeSciences, funded by AMAG Pharmaceuticals, Inc.


                ida, phosphate, hypophosphatemia, iron supplementation


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