What are the contra-indications to iron tablets in patients with Iron Deficiency Anemia (IDA)?

Contraindications to Iron Tablets in Iron Deficiency Anemia

Iron tablets should not be used in patients with active inflammatory bowel disease, as systemic inflammation inhibits iron absorption through hepcidin elevation, making oral iron ineffective and potentially harmful. 1

Absolute Contraindications

Active Inflammatory Disease

• Patients with active IBD should not receive oral iron tablets because inflammation-induced hepcidin elevation severely impairs intestinal iron absorption 1
• In IBD patients with hemoglobin <10 g/dL and active disease, intravenous iron is first-line therapy, not oral iron 1
• Oral iron may worsen intestinal inflammation in active IBD 2

Imminent Colonoscopy

• Iron replacement therapy should not be deferred while awaiting investigations unless colonoscopy is imminent, as iron can interfere with visualization 1

Concurrent Antibiotic Use

• Iron tablets should not be taken within two hours of certain antibiotics, as oral iron products interfere with antibiotic absorption 3

Relative Contraindications and Cautions

Severe Symptomatic Anemia with Hemodynamic Instability

• Oral iron is contraindicated when rapid correction is needed for severe, symptomatic IDA with circulatory compromise 1, 4
• In these cases, packed red cell transfusion followed by iron replacement (preferably IV) is appropriate 1

Conditions Affecting Iron Absorption

While not absolute contraindications, oral iron is relatively contraindicated and IV iron should be strongly considered in:

• Post-bariatric surgery patients due to disrupted duodenal absorption mechanisms 1, 2
• Celiac disease with ongoing gluten exposure where malabsorption persists 1
• Chronic kidney disease with functional iron deficiency where oral absorption is impaired 1

Intolerance to Multiple Oral Formulations

• After documented intolerance to at least two different oral iron preparations (ferrous sulfate, fumarate, or gluconate), continuing oral iron is contraindicated 1
• Switch to IV iron rather than trying additional oral formulations 2

Important Safety Warnings from FDA Labeling

• Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6 - products must be kept out of reach of children 3
• Oral iron should not exceed recommended dosage 3
• Treatment of any anemic condition should be under physician supervision 3

Clinical Algorithm for Oral Iron Use

Step 1: Assess for Active Inflammation

• If active IBD or other inflammatory condition with hemoglobin <10 g/dL → Use IV iron, not oral 1
• If inactive disease → Oral iron acceptable 1

Step 2: Evaluate Absorption Capacity

• Post-bariatric surgery → Prefer IV iron 1, 2
• Active celiac disease → Prefer IV iron 1
• Normal GI anatomy and no inflammation → Oral iron appropriate 1

Step 3: Check for Imminent Procedures

• Colonoscopy scheduled within days → Defer oral iron 1
• Otherwise → Start oral iron immediately 1, 2

Step 4: Assess Severity

• Severe symptomatic anemia with hemodynamic instability → Transfusion + IV iron, not oral 1, 4
• Stable patient → Oral iron appropriate 1

Common Pitfalls to Avoid

• Do not prescribe oral iron to patients with active IBD, especially if hemoglobin <10 g/dL - this is ineffective and potentially harmful 1
• Do not continue oral iron in patients who fail to respond after 4 weeks - reassess for malabsorption, inflammation, or ongoing blood loss and switch to IV iron 1
• Do not exceed 100 mg elemental iron daily in patients with inactive IBD, as higher doses may trigger inflammation 1
• Do not give oral iron within 2 hours of antibiotics due to absorption interference 3
• Do not use oral iron as first-line in post-bariatric surgery patients - anatomic changes make IV iron more appropriate 1, 2

When Oral Iron Becomes Contraindicated During Treatment

• Development of intolerance despite trying ferrous sulfate, fumarate, and gluconate 1
• Failure of ferritin to improve after 4 weeks of compliant therapy 2
• Failure of hemoglobin to rise by at least 10 g/L after 2 weeks of daily therapy 1
• Development of active inflammatory disease during treatment 1
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity 2