Background and purpose: To evaluate in RLS patients the efficacy and safety of repeated infusions of iron in order to maintain symptomatic improvements achieved with a prior single 1000 mg infusion of iron.
Patients and methods: Subjects who had demonstrated initial improvement in RLS symptoms after a single 1000 mg infusion of iron were evaluated monthly for serum ferritin and RLS severity. If symptoms returned at any time in the 2-year period after initial iron treatment, supplemental 450 mg iron gluconate infusions could be given, provided the ferritin was <300 mcg/l. The primary outcome measures were side effect profile, duration (weeks) of sustained improvement, and rate of change of serum ferritin.
Results: Ten subjects received the initial single 1000 mg dose of iron dextran, but only five subjects were eligible to receive supplemental iron infusions. RLS symptoms returned on average 6 months after the initial 1000 mg infusion. Because of noncompliance with monthly visits one subject was dropped after receiving three supplemental iron infusions. Because of a ferritin >300 mcg/l, a second subject was dropped after having received one supplemental treatment. Three subjects completed the 2-year period of the study, having received between two and four courses of supplemental iron. After the initial 1000 mg iron infusion, the ferritin declined on average 6.6 mcg/l/week, which was substantially higher than the predicted value of <1 mcg/l per week. The rate of ferritin decline decreased toward normal with repeated IV iron treatments: the average rate of decline in ferritin for the last treatment course was 2.3 mcg/l/wk. The slower the rate of ferritin decline the more prolonged the symptom improvements.
Conclusions: Supplemental iron treatments can sustain previously achieved improvements with a single IV iron treatment, but achieving high ferritin levels was not in themselves a guarantee of sustained improvements. The most notable finding was the post-infusion changes in serum ferritin and its implication for altered iron excretion.