Relationship Between Initial Parenteral Iron Therapy Dosing and Treatment Effectiveness: A Real-World Retrospective Analysis.

Purpose: Replacement iron is the main treatment for iron deficiency, but the relationship between initial intravenous (IV) dose and need for additional treatment is unclear. This study explored patterns of IV iron dosing in US clinical practice. Methods: Patient records were obtained for adults who received IV iron for anemia between 2015 and 2017. Patients were classified into four groups: those who received <1500 mg and ≥1500 mg IV iron and those received ≤1000 mg and >1000 mg within 3 weeks of their first dose. The proportion of patients requiring additional IV iron after 30 days of the initial dose was evaluated. Results: Data were obtained for 2959 patients receiving iron sucrose (44.2%), ferric carboxymaltose injection (FCM) (25.8%), and ferumoxytol (FM) (14.3%). Overall, 567 patients (19%) received ≥1500 mg of IV iron and 942 (32%) received >1000 mg of IV iron within the first 21 days. Mean (SD) baseline iron deficit was 1001 mg (312). Patients who received ≥1500 mg had a 32% lower probability of receiving additional IV iron than those who received <1500 mg (adjusted hazard ratio [HR]: 0.68 [95% confidence interval (CI); 0.58, 0.81]) and incurred significantly fewer outpatient visits for all causes (p < 0.001) and IV iron treatment (p < 0.001). Patients who received an initial dose of >1000 mg had a 41% lower probability of receiving additional IV iron than those who received ≤1000 mg (adjusted HR: 0.59 [95% CI; 0.52, 0.67]) and had significantly fewer outpatient visits for all causes (p < 0.001) and IV iron treatment (p < 0.001). Patients receiving FCM required fewer outpatient visits than those receiving FM and other treatments, including a subgroup of patients who initially received >1000 mg IV iron. Conclusion: Higher doses of IV iron within 3 weeks of first dose may reduce further IV iron treatment needs and outpatient visits.