A randomized controlled trial comparing oral and intravenous iron supplementation after Roux-en-Y gastric bypass surgery.

Background: Iron deficiency (ID) is one of the most common postoperative deficiencies that may develop after Roux-en-Y gastric bypass (RYGB). The optimal mode of treatment is uncertain. Aim: To compare the efficacy of oral ferrous fumarate (FF), oral ferrous gluconate (FG), and a single intravenous infusion of ferric carboxymaltose (FCM) in women with ID after RYGB.

Methods: Multicenter randomized controlled trial including 120 women with a serum ferritin <20 μg/l during follow-up after RYGB. They were randomized into three groups: 41 patients were treated with FF 200 mg three times a day (total daily dose: 195 mg elemental iron), 39 received FG 695 mg twice a day (total daily dose: 160 mg elemental iron) for three months, and 39 patients were treated with a single intravenous dose of FCM (1000 mg elemental iron). Serum ferritin levels were measured at six weeks, and three, six and twelve months after the start of supplementation.

Results: At three months, persistence of ID was observed in 29.4% and 42.4% of the patients treated with FF and FG, respectively, but in none of those treated with FCM (p < 0.001). Over the next nine months, recurrence of ID was observed in 56.5% of patients treated with FF, in 52.9% treated with FG, and in 27.8% of those treated with FCM. Adverse effects were most common during oral treatment.

Conclusion: In women developing ID after RYGB, a single dose of intravenous FCM is more effective and better tolerated than the standard treatment with either FF or FG. Clinical trial registry number and website: The study was registered at clinicaltrials.gov under number NCT02271997.