Ferric carboxymaltose in patients with restless legs syndrome and nonanemic iron deficiency: A randomized trial

Trenkwalder C

Published in Movement Disorders

Methodology

Randomised placebo-controlled trial in iron-deficient non-anaemic patients with moderate to severe restless legs syndrome; single intravenous dose of ferric carboxymaltose (1000 mg iron) or placebo; primary endpoint mean change difference in IRLS severity score from baseline to week 4, with week 12 as secondary endpoint.

Key Findings

110 patients with moderate to severe restless legs syndrome and iron deficiency without anaemia (ferritin under 75 microgram/L, or 75-300 with transferrin saturation under 20%) were randomised to a single 1000 mg intravenous dose of ferric carboxymaltose (n = 59) or placebo (n = 51). The improvement in the International Restless Legs Syndrome Severity Scale at week 4, the primary endpoint, was not significant (difference -2.5, 95% CI -5.93 to 1.02, p = 0.163). By week 12, a secondary endpoint, the difference reached significance (-4.66, 95% CI -8.59 to -0.73, p = 0.021). The authors conclude intravenous iron may need longer than assumed to stabilise symptoms.

Conclusions

Intravenous iron benefit emerged only by week 12; the week-4 primary endpoint was not met.

Limitations

The trial missed its primary endpoint at week 4 and the positive result comes from a secondary timepoint, so it should be treated as hypothesis-generating; the study was funded and co-authored by the manufacturer of the iron preparation.