Emerging causes of iron deficiency anemia refractory to oral iron supplementation

Abstract

While oral iron supplementation is commonly used throughout many clinical setting, treatment with intravenous (IV) iron has historically been reserved for specific settings, such as chronic kidney disease, gynecologic issues, and anemia associated with cancer and its treatments. However, the use of IV iron has begun to gain popularity in the treatment of iron deficiency anemia (IDA) associated with two conditions that are being seen more frequently than in years past: patients who are status post gastric bypass procedure and those with inflammatory bowel disease (IBD). The Roux-en-Y procedure involves connecting a gastric pouch to the jejunum, creating a blind loop consisting of distal stomach, duodenum, and proximal jejunum that connects to the Roux limb to form a common tract. IDA occurs in 6%-50% of patients who have undergone a gastric bypass, the etiology being multifactorial. The proximal gastric pouch, the primary site of gastric acid secretion, is bypassed, resulting in a decreased ability to metabolize molecular iron. Once metabolized, most iron is absorbed in the duodenum, which is entirely bypassed. After undergoing bypass procedures, most patients significantly limit their intake of red meat, another factor contributing to post-bypass IDA. Chronic anemia occurs in approximately 1/3 of patients who suffer from IBD, and almost half of all IBD patients are iron deficient. IBD leads to IDA through multiple mechanisms, including chronic intestinal blood loss, decreased absorption capabilities of the duodenum secondary to inflammation, and an inability of many IBD patients to tolerate the side effects of oral ferrous sulfate. In this study, we reviewed the charts of all patients who received IV iron at Sylvester Comprehensive Cancer Center/University of Miami Hospital Clinic from January 2007 to May 2012. The most common indications for IV iron were for issues related to cancer and its treatment (21.9%), IBD (20.1%), and gastric bypass (15.0%). Of the 262 patients who received IV iron, 230 received iron sucrose and 36 received iron dextran. While doses of 100, 200, 300, and 400 mg of iron sucrose were given, 100 and 200 mg were by far the most common dosages used, 122 and 120 times, respectively. The number of dosages of iron sucrose given ranged from 1 to 46, with a mean of 5.5 and a median of 4 doses. The average dose of iron dextran given was 870.5 mg, with 1000 mg being the most common dosage used. Most patients (22 of 36) who received iron dextran only received one dose. While patients with traditional indications for IV iron, such as gynecologic issues and kidney disease, still were represented in this study, we expect to see a continued increase in physicians using IV iron for emerging gastrointestinal indications, especially considering the increased safety of new low-molecular formulations.

Keywords: Anemia; Iron deficiency anemia; Intravenous iron; Gastric bypass; Inflammatory bowel disease; Crohn’s disease; Ulcerative colitis; Chemotherapy-associated anemia

Core tip: Decreased absorption of oral iron leading to iron deficiency is a significant cause of anemia in several patient groups, including those status post gastric bypass surgery and those with inflammatory bowel disease. In these patients, oral iron supplementation is unlikely to correct the deficiency. Intravenous iron is a safe, effective treatment strategy for overcoming the iron deficit seen in these patients, resulting in better outcomes and improved quality of life.