Treatment with intravenous ferric carboxymaltose significantly improved symptoms in restless legs syndrome (RLS) patients with iron-deficiency anemia (IDA), data from 29 adults show.
RLS occurs among individuals with normal iron but is at least six times higher among individuals with IDA, Hyoeun Bae, MD, of Keimyung University, Daegu, South Korea, and colleagues wrote. Previous studies have explored iron treatments for RLS patients with IDA, however, guidelines for treatment have not yet been published.
In a study published in Sleep Medicine, the researchers randomized 29 RLS patients with IDA to either 1,500 mg IV ferric carboxymaltose (FCM) or placebo for a short-term period of 6 weeks, followed by a phase 2 study for responders that lasted for 52 weeks. Baseline characteristics, including age, gender, iron parameters, and sleep and mood scales were similar between the groups.
At 6 weeks, patients in the FCM group showed significant improvement in RLS symptom severity based on changes from baseline International Restless Legs Syndrome Study Group scale (IRLS) scores, compared with placebo patients (–13.47 vs. 1.36, P < .001). A secondary outcome of sleep quality also improved significantly in the FCM group, compared with the placebo group.
After 6 weeks, 11 of the 14 patients in the placebo group also received 1,500 mg FCM for an open-label study. These patients also showed significant improvement in IRLS scores from baseline to 6 weeks.
All 23 responders from the short-term studies (13 who received FCM initially and 10 from the postplacebo group) enrolled in a phase 2 long-term study that lasted for 52 weeks; 14 of these completed the full 52-week study period.
Overall, 61% of participants in phase 2 of the study remained off their RLS medications at 52 weeks, and no serious adverse events were reported during the study period. Of these, 10 received one additional dose of FCM and 4 received more than one additional dose. The median change in IRLS score at 4 weeks after treatment was –4.00, compared with the score prior to treatment.
The study is the first of its design to show benefits of intravenous iron therapy for RLS in patients with IDA, the researchers said, noting that the findings of improved, but not cured, RLS symptoms might suggest that more than 1,500 mg of iron is needed to fully treat RLS in this patient population. “A second interpretation is that the RLS and IDA were separate events: a patient with idiopathic RLS who subsequently developed anemia,” they said. “Treating the IDA might improve symptoms but may not eliminate the symptoms.”
The study findings were limited by several factors, including the relatively small study population and inability to know the time frame for the development of IDA, the researchers noted. However, the results support the use of intravenous iron therapy for relief of RLS in IDA patients.
“Since IDA could result in epigenetic changes leading to irreversible state of RLS, then urgent and adequate management of the IDA in RLS patients would seem a very prudent and important clinical approach to this specific clinical condition,” they concluded.
The study received no outside funding. The researchers had no disclosures.