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.