## IV Iron in Oral Intolerance ### Indications for Parenteral Iron **Key Point:** When oral iron is not tolerated due to GI side effects, IV iron is the next step. Ferric carboxymaltose is preferred among IV agents due to rapid infusion, single-dose repletion potential, and lower anaphylaxis risk. ### Comparison of IV Iron Formulations | Agent | Dose per infusion | Frequency | Half-life | Anaphylaxis risk | Advantage | | --- | --- | --- | --- | --- | --- | | **Ferric carboxymaltose** | 750 mg | 1–2 doses | 7–12 h | Very low (<0.1%) | Rapid infusion, complete repletion in 1–2 doses | | **Iron sucrose** | 200 mg | 3× weekly | 6 h | Very low | Safe in CKD, preferred in dialysis patients | | **Iron dextran** | 100–500 mg | Daily/weekly | 3–4 weeks | Moderate (0.6–0.7%) | Longer half-life, but obsolete | | **Ferumoxytol** | 510 mg | 2 doses | 15 h | Low | Rapid infusion, but less available | **High-Yield:** Ferric carboxymaltose can replicate total iron stores in 1–2 infusions, whereas iron sucrose requires multiple weekly infusions. For non-dialysis patients with oral intolerance, ferric carboxymaltose is preferred. ### Clinical Pearl **Clinical Pearl:** Iron sucrose is the agent of choice specifically in **chronic kidney disease patients on hemodialysis** because it has minimal risk of anaphylaxis and is used as maintenance therapy. However, in this non-dialysis patient with acute GI intolerance, ferric carboxymaltose is superior due to rapid repletion. ### Mechanism of GI Side Effects Oral iron causes: - Direct mucosal irritation → nausea, vomiting, abdominal pain - Increased intestinal permeability → diarrhea or constipation - Reactive oxygen species generation → mucosal inflammation **Mnemonic:** **SCAB** — Sucrose (dialysis), Carboxymaltose (Acute non-dialysis), Both IV.
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