Clinical efficacy of ferric carboxymaltose treatment in patients with restless legs syndrome

Abstract

Objective: There have been three randomized, placebo-controlled, double-blind studies of intravenous iron in restless legs syndrome (RLS), with differing outcomes. The one positive study used ferric carboxymaltose (FCM) at a total dose of 1000 mg. The purpose of this study was to replicate and extend the findings from the prior FCM study.

Methods: Non-anemic, idiopathic RLS patients were enrolled in a randomized, double-blinded, placebo-controlled study and received either 1000 mg FCM or placebo as a single infusion (phase I). Subjects were off any RLS medications for at least two weeks prior to baseline assessment. The primary outcome variable was change from baseline at week 6 on the International Restless Legs Syndrome Severity (IRLSS) scale and a subject-completed, visual analog scale (VAS) of severity. Phase II of the study involved long-term (30 weeks) follow-up after completion of the six-week efficacy phase.

Results: At week 6 postinfusion, FCM compared to placebo recipients showed significantly greater change from baseline for both primary outcome measures (IRLSS scale, -11.9 ± 8.04 vs -7.88 ± 5.89, p = 0.03; VAS, -40.6 ± 22.7 vs -21.3 ± 20.0, p = 0.001). None of the secondary outcome variables showed a significant difference at week 6. After six weeks of treatment, the FCM group had 19 (59.4%) responders, of which 12 had IRLSS scores <10 ("remitters"). Twelve (37.5%) of the 32 subjects treated with iron in phase I remained free of further RLS medications at 30 weeks. There were no serious adverse events observed in this study.

Conclusion: Two studies now support the value of FCM treatment both in the short term (six weeks) and long term (30 weeks) for improving RLS symptoms.

Keywords: IV ferric carboxymaltose; Restless legs syndrome; Treatment.