A randomized double-blind pilot study to evaluate the efficacy, safety, and tolerability of intravenous iron versus oral iron for the treatment of restless legs syndrome in patients with iron deficiency anemia.

Restless legs syndrome (RLS) is a neurological disorder that can have a profound effect on sleep and quality of life. Idiopathic RLS is associated with brain iron insufficiency despite normal peripheral iron stores. There is, however, a five- to six-fold increase in prevalence of RLS in patients with iron deficiency anemia (IDA). Several open-label trials have demonstrated symptomatic improvement in RLS following treatment of IDA using oral or intravenous iron supplementation. To date, there have been no randomized double-blind controlled trials of intravenous iron compared with oral iron for the treatment of RLS patients with IDA. In the current study, oral ferrous sulfate and ferumoxytol were compared for efficacy and speed of response for treatment of RLS occurring in patients with IDA. The planned recruitment for this study was 70 patients with RLS and IDA, to be randomly assigned 1:1 to oral or intravenous iron, using double-blind, double-dummy procedures. At Week 6, the primary outcomes of Clinical Global Impression-Improvement score and change from baseline in the International Restless Legs Syndrome Study Group rating scale score were assessed. Due to challenges, performing the clinical trial during the COVID-19 pandemic, final-week data were found missing for 30 patients. As a result, in order to maintain the prespecified statistical analysis, an additional 30 patients were recruited. Both IV and oral iron were associated with a marked improvement in RLS symptoms, with no statistically significant difference between treatment groups. No serious adverse events were observed in either treatment group.

Safety and efficacy of total dose infusion of 1,020 mg of ferumoxytol administered over 15 min.

For the majority of patients with iron deficiency anemia (IDA), a full course of intravenous (IV) iron is 1 g. Most IV irons require 5-10 administrations of 100-300 mg. We have successfully employed 1 g low molecular weight iron dextran over 1 hr. For further convenience for patients and physicians, we explored the administration of 1.02 g of ferumoxytol over 15 min instead of the approved 2 × 510 mg injections. Sixty patients with IDA, (hemoglobin <11 g/dL, transferrin saturation [TSAT] ≤20%, and ferritin <100 ng/mL) with an inadequate response or intolerance to oral iron, received 1020 mg ferumoxytol over 15 min. Vital signs were measured for 1 hr. Adverse events (AEs) were collected via telephone at 1, 2, and 7 days. Follow-up visits occurred at 4 and 8 weeks for efficacy assessments. The primary endpoint was safety and tolerability. Secondary efficacy endpoints included mean change in hemoglobin, TSAT, and red cell distribution width. No serious adverse events (SAEs) occurred. Fifty-eight patients received the planned dose. Twenty-six out of sixty (43.3%) patients reported AEs of which 13 were mild and transient during infusion. All resolved within minutes. Fourteen patients reported self-limited arthralgias, myalgias, and/or headache within 24-48 hr. At Baseline, the mean hemoglobin was 9.4 g/dL. The mean increments at Week 4 and 8 were 2.1 and 2.6 g/dL, respectively. Ferumoxytol, administered as 1.02 g infusion over 15 min was well tolerated with no SAEs and demonstrated excellent efficacy. If corroborated in future studies this represents an improved method of treating IDA.