What are the recommendations for iron infusion in a 71-year-old female with chronic anemia, unable to tolerate oral iron, with hypoferritinemia (low ferritin level), and iron deficiency, and when should iron studies be repeated?

Iron Infusion Recommendations for a 71-Year-Old Female with Chronic Anemia

Intravenous iron therapy is strongly recommended for this patient with iron deficiency who is unable to tolerate oral iron, with a preferred approach of using formulations that can replace iron deficits in 1-2 infusions. 1

Diagnosis Assessment

The patient presents with clear evidence of iron deficiency:

• Ferritin level of 25 ng/mL (below the 30 ng/mL threshold for definitive iron deficiency)
• Low serum iron level of 28
• Low transferrin saturation (calculated as iron/TIBC × 100 = 28/343 × 100 = 8.2%, well below the 20% threshold)
• Hemoglobin of 10.8 g/dL indicating mild anemia
• Negative upper and lower endoscopies ruling out obvious GI bleeding sources

Iron Infusion Recommendations

Number of Infusions

1. Single or two-dose approach is preferred 1, 2

   • According to the American Gastroenterological Association (AGA), "intravenous iron formulations that can replace iron deficits with 1 or 2 infusions are preferred over those that require more than 2 infusions" 1
   • Options include:
     • Ferric carboxymaltose: Can be administered as a single dose of up to 1000 mg infused over 15 minutes 2, 3
     • Iron dextran: Can replenish iron in a single infusion but carries a higher risk of reactions (0.6-0.7%) 2

2. Dosing calculation

   • Total iron deficit can be calculated using the Ganzoni formula:
     • Total iron deficit (mg) = Body weight (kg) × (Target Hb - Actual Hb) × 2.4 + 500 mg (for iron stores)
   • For this patient with mild anemia, a single dose of 750-1000 mg would likely be sufficient 3

Safety Considerations

• All IV iron formulations have similar safety profiles, with true anaphylaxis being very rare 1
• Most reactions are complement activation-related pseudo-allergy (infusion reactions) 1
• Monitor vital signs during and after infusion
• Have resuscitation equipment available during administration

Monitoring Recommendations

When to Repeat Iron Studies

1. Initial follow-up at 4 weeks

   • Check hemoglobin and iron studies 4 weeks after IV iron administration to assess initial response 2
   • Expect an increase in hemoglobin of at least 1 g/dL within 4 weeks of treatment 2

2. Subsequent monitoring

   • Iron studies should be repeated every 3 months during the maintenance phase 2
   • This allows for timely identification of recurrent iron deficiency and appropriate re-treatment

3. Re-treatment criteria

   • Re-treatment should be initiated when serum ferritin drops below 100 μg/L 2
   • Or if hemoglobin falls below gender-specific thresholds
   • Or if symptoms of iron deficiency recur

Common Pitfalls to Avoid

1. Inadequate dosing

   • Underdosing IV iron may lead to incomplete correction of iron deficiency and persistent symptoms
   • Single large-dose formulations are preferred over multiple small doses 1

2. Premature discontinuation of monitoring

   • Iron deficiency may recur, especially if the underlying cause persists
   • Regular monitoring every 3 months is essential 2

3. Mistaking infusion reactions for anaphylaxis

   • Most reactions are complement activation-related pseudo-allergy, not true anaphylaxis 1
   • Appropriate management differs between these conditions

4. Failure to investigate underlying cause

   • Despite negative endoscopies, continued investigation for the cause of iron deficiency is warranted
   • Consider other sources of blood loss, malabsorption, or nutritional deficiencies

By following these recommendations, this 71-year-old patient with chronic anemia and iron deficiency who cannot tolerate oral iron should achieve improvement in hemoglobin levels and reduction in anemia-related symptoms.