Introduction Restless legs syndrome (RLS) is a common debilitating neurological disorder. Midbrain iron deficiency has been implicated in the pathophysiology of RLS. There is evidence that supports the use of ferric carboxymaltose (FCM) in ameliorating RLS severity. This study aims to evaluate the effectiveness of FCM in a cohort with refractory RLS.
Methods Clinically eligible patients with diagnosed RLS from Guy’s Sleep Disorder Centre, who received single-dose FCM 1000mg as per clinic protocol between January 2020 and January 2023 were included. Electronic patient records were retrospectively reviewed. Ferritin levels and percentage transferrin saturation (TSat%) were recorded at baseline and at 12-weeks post-infusion of FCM. The severity of RLS symptoms as per International RLS Study Group rating scale (IRLS) (range 0–40), was recorded at the same intervals.
Results Twenty patients (age 51.1±16, 15 female) were identified, with a mean IRLS score of 22.1 ±4.3 and ferritin of 40.9±18.2mcg/L. Ten patients (50%) had a history of anxiety/depression, six (30%) had a history of OSA, and eleven (55%) had unsuccessfully trialled dopamine agonists and gabapentinoids for RLS.
At 12-weeks the mean ΔIRLS score was -9.4±1.7 (p=0.001), mean Δferritin was 195.4±96.6mcg/L (p<0.001), and ΔTSat% was 9.8±3.2 (p=0.007).There was a significant negative correlation at 12-weeks between post-infusion ferritin levels and the mean IRLS score (Pearson correlation coefficient= −0.71, p< 0.001).
Twelve patients (60%) reported improvement of RLS symptoms at week-12, with five patients (25%) reporting complete resolution of symptoms of which three patients stopped their RLS-medications. Non-responders (table 1) did not report symptom deterioration at week-12 compared to baseline. There were no infusion-related serious adverse events reported; there was one minor side effect reported which self-resolved (fever).
Conclusion Intravenous FCM conferred significant symptomatic improvement in the majority of patients with severe refractory RLS. The infusion was well tolerated. Further studies are warranted to investigate non-response.
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