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Aliment Pharmacol Ther. 2019 Aug;50(4):397-406. doi: 10.1111/apt.15386. Epub 2019 Jul 2.

Incidence of hypophosphatemia in patients with inflammatory bowel disease treated with ferric carboxymaltose or iron isomaltoside.

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Department of Gastroenterology, Akershus University Hospital, Lørenskog, Norway.
Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Health Services Research Unit, Akershus University Hospital, Lørenskog, Norway.
Division of Medicine, Department of Gastroenterology, Oslo University Hospital Ullevål, Oslo, Norway.
Department of Medicine II, Gastroenterology and Hepatology, Medical University of Innsbruck, Innsbruck, Austria.



Iron deficiency and iron deficiency anaemia are common complications in inflammatory bowel disease (IBD). In patients with moderate-to-severe anaemia, oral iron intolerance or ineffectiveness of oral iron, ferric carboxymaltose and iron isomaltoside are widely used. Hypophosphatemia is a side effect of both preparations.


To investigate the occurrence of hypophosphatemia in IBD patients with iron deficiency/iron deficiency anaemia treated with high-dose intravenous iron.


A prospective observational study of adult IBD patients with iron deficiency/iron deficiency anaemia was conducted at two study sites where patients received 1000 mg of ferric carboxymaltose or iron isomaltoside. At baseline, weeks 2 and 6, blood and faecal samples were collected. The primary endpoint was to determine the incidence of moderate-to-severe hypophosphatemia. Secondary endpoints included the total incidence of hypophosphatemia, possible risk factors for hypophosphatemia, and response to single-dose intravenous iron.


One hundred and thirty patients were included. In the per-protocol set, 52 patients received ferric carboxymaltose and 54 patients received iron isomaltoside. Ferric carboxymaltose treatment had a significantly higher incidence of moderate-to-severe hypophosphatemia compared with iron isomaltoside at week 2 (56.9% vs 5.7%, P < 0.001) and a higher incidence at week 6 (13.7% vs 1.9%, P = 0.054).The overall incidence of hypophosphatemia was significantly higher with ferric carboxymaltose compared with iron isomaltoside treatment at weeks 2 (72.5% vs 11.3%, P < 0.001) and 6 (21.6% vs 3.7%, P = 0.013).


In IBD patients with iron deficiency/iron deficiency anaemia, ferric carboxymaltose was associated with higher incidence, severity and persistence of hypophosphatemia compared with iron isomaltoside. The presence of moderate-to-severe hypophosphatemia beyond 6 weeks is a clinical concern that requires further investigation.


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