Z Gastroenterol 2016; 54 - P51
DOI: 10.1055/s-0036-1584029

Choice of High-Dose Intravenous Iron Preparation Determines Hypophosphatemia Risk – A Retrospective Cohort Study

B Schaefer 1, P Würtinger 2, A Finkenstedt 1, V Braithwaite 3, M Effenberger 4, A Moschen 4, A Griesmacher 2, H Tilg 4, W Vogel 1, H Zoller 1
  • 1Medical University of Innsbruck, Department of Medicine II, Gastroenterology and Hepatology, Innsbruck, Austria
  • 2Central Institute for Medical and Chemical Laboratory Diagnosis, Innsbruck University Hospital, Innsbruck, Austria
  • 3Medical Research Council (MRC) Human Nutrition Research, Elsie Widdowson Laboratories, Cambridge, United Kingdom
  • 4Medical University of Innsbruck, Department of Medicine I, Gastroenterology, Endocrinology and Metabolism, Innsbruck, Austria

Ferric carboxymaltose (FCM) and iron isomaltoside 1000 (IIM) allow complete correction of iron deficiency in a single infusion. Recent reports have raised concerns that iron substitution with FCM can induce hypophosphatemia. Gastroenterology clinic patients are at risk of hypophosphatemia due to malabsorption or vitamin D deficiency and are frequently treated with high-dose intravenous iron.

The aim of this retrospective study was to assess the prevalence and determinants of iron-induced hypophosphatemia. Five hundred and thirty-nine documents containing the keywords ferric carboxymaltose (FCM) or iron isomaltoside 1000 (IIM) were retrieved by searching electronic medical records. Documented administration of FCM or IIM with plasma phosphate concentrations before and after treatment were available for 80 patients (14.8%). The concentration of intact (iFGF-23) and C-terminal fibroblast growth factor (cFGF-23), parathyroid hormone, 25-hydroxy and 1,25-dihydroxy-vitamin D were measured in archival samples.

The prevalence of hypophosphatemia (< 0.8 mmol/L) increased from 10% (8 of 80 patients) to 31.3% (25 of 80) after treatment with FCM or IIM. The risk of developing hypophosphatemia was greater after FCM compared with IIM (44% vs. 4% respectively). Severe hypophosphatemia (< 0.6 mmol/L) occurred exclusively after treatment with FCM (29.8%). A significant increase in the active form of the phosphate regulating hormone FGF-23 was observed after i.v. iron treatment in patients who developed hypophosphatemia.

In conclusion, treatment with FCM is associated with a high risk of developing severe hypophosphatemia. Despite equal efficacy in correction of iron deficiency, the hypophosphatemia risk appears to be substantially lower with IIM.