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Iron for RLS

Clinical bottom line

Limited data suggests that intravenous iron dextran may have utility for patients with end stage renal disease who also have RLS.


References

BJ David et al. A randomized, double-blind placebo-controlled trial of iron in restless legs syndrome. European Neurology 2000 43: 70-75.

JA Sloand et al. A double-blind, placebo-controlled trial of intravenous iron dextran therapy in patients with ESRD and restless legs syndrome. American Journal of Kidney Diseases 2004 43: 663-670.

Clinical trials

Two small randomised trials were found. One examined oral iron sulphate supplementation in patients with restless legs syndrome with no secondary cause. The other examined a single intravenous infusion of iron dextran in patients with end stage renal disease on dialysis.

Results

Table 1 has the details of the studies. Oral iron sulphate was without effect. In patients with end-stage renal disease a single intravenous infusion of iron dextran, but not placebo, reduced RLS symptom scores by about half over about one to four weeks. Patients receiving iron dextran had significant increases in their serum ferritin levels.

Table 1: Clinical trials with iron supplementation

Reference
Design
Treatments and Outcomes
Patient details
Efficacy
Adverse Events
Davis et al. Eur Neurol 2000 43: 70-75 R = 1
DB = 2
WD = 1
QS = 4
Parallel group
Duration = 14 weeks
Treatments
1 Ferrous sulphate 650 mg daily in liquid form (14)
2 Placebo solution (14)

Outcomes
Sleep and RLS symptoms using VAS scales
Patients were about two-thirds women, with an average age of 59 years (range 33-80). Mean Hb at start was 140 g/L, and ferritin 120 g/L. No significant differences were seen for sleep quality or RLS symptoms Adverse events were seen only in patients taking iron sulphate (nausea, constipation, darkened stool tooth discolouration, vertebral fracture, worsening of RLS and bladder spasms)
Sloand et al. Am J Kidney Dis 2004 43: 663-670. R = 1
DB = 1
WD = 1
QS = 3
Parallel group
Duration = 4 weeks
Treatments
1 Single dose of 1000 mg iron dextran IV (11)
2 Placebo IV (14)

Outcomes
Rating scales for RLS symptoms
Patients with end stage renal disease (age range 36-74) undergoing haemodialysis of (one patient) peritoneal dialysis Lower baseline ferritin levels were related to higher RLS symptom score. RLS scores fell significantly at 1, 2 and 4 weeks with iron dextran, but not after placebo infusion. Ferritin levels rose with iron dextran, but not placebo AE reported in 10/11 with iron dextran and 8/14 with placebo

 

Comment

These two trials are interesting, and different, but very small and of limited duration, so too much should not be made of too little. In the first trial in patients with RLS of no secondary cause, mean haemoglobin levels were about 140 g/L, while those with RLS on dialysis in the second trial had lower haemoglobin levels, of about 110 g/L. It is not entirely surprising that an effect was seen in the short term in the latter but not the former, especially as iron metabolism is implicated in RLS.