Currently, in many centres,
intravenous administration of
iron is becoming increasingly popular because of higher efficacy and decreased side effects, mainly gastrointestinal, compared with oral
iron therapy. Studies of intravenous
ferric carboxymaltose administration in the postpartum setting and in patients with non-dialysis-dependent
chronic kidney disease revealed a decrease in serum
phosphate levels that was generally asymptomatic and transient. Here, we report four cases of severe and symptomatic hypophosphataemia after intravenous
iron administration. All patients received this as
therapy for
iron deficiency anaemia due to
heavy menstrual bleeding. In most cases, a pre-existent disorder in the
phosphate homeostasis existed, such as a secondary (cases 3 and 4) or tertiary
hyperparathyroidism (case 1). However, in the second case there were no risk factors for a dysregulation of the
phosphate homeostasis. Based on these findings, we conclude that severe and symptomatic
hypophosphatemia can occur as a side effect of intravenous
iron administration and can persist for months after administration. Especially patients with low
phosphate levels prior to
therapy due to concomitant disorders in
phosphate homeostasis (e.g.
hyperparathyroidism,
vitamin D deficiency) are at risk.