Background and Importance Hypophosphatemia after intravenous ferric carboxymatose (FCM) is a well-documented adverse reaction. However, there is scant evidence about its prevalence among elderly patients with hip fracture, a complex polymedicated pluripathologic population exposed to these formulations in perioperative care.

Aim and Objectives The aim of this study was to identify the incidence of hypophosphatemia in patients over 65 years old treated with FCM in the context of hip surgery.

Material and Methods Observational retrospective study including all patients admitted to the Orthogeriatric Unit of a tertiary hospital from June 2023 to August 2023 for hip fracture and treated with FCM. Analytical treatment-related data were collected from electronic medical records. For descriptive analysis, categorical variables are presented as counts and percentages. Continuous variables as medians and interquartile range.

Results 65 patients were included (51/65[78.5%] women, 88±7 years old), with a median hospital stay of 13 days. The total doses used were 500 mg (69.2% of patients), 1 g (24.6%) or higher. On the gathered data are shown elevated parathormone and low cholecalciferol levels, and an altered glomerular filtration rate. Of the patients included, 28 had both pre- and post-iron administration phosphate levels measured. Among them, 21 (75%) experienced a phosphate level reduction with a mean change of -36.4[19.1–51.4]% from their initial levels to the second measurement, mirroring the overall trend shown in the table 1. Within this group, 5 out of 28 patients (17.9%) had initial phosphate levels below 2.5 mg/dL. After iron administration, this increased up to 12 (42.9%). None of them showed any relevant clinical signs associated.

Conclusion and Relevance Blood phosphate levels tend to decrease notably after FCM administration, suggesting a potential correlation. However, hyperparathyroidism and vitamin D deficiency are common in this population and may also influence this outcome. Phosphatemia monitoring and phosphate supplementation are measures that need to be considered to reduce possible clinical consequences, especially in elderly patients with additional risk factors.

Conflict of Interest No conflict of interest.