How should I prescribe intravenous iron for an adult patient with hemoglobin 7 g/dL?

Prescribing Intravenous Iron for a Patient with Hemoglobin 7 g/dL

For a patient with hemoglobin 7 g/dL, you should administer intravenous iron at a total dose of 1,500-2,000 mg based on body weight, given either as two divided doses of 750 mg separated by at least 7 days, or as a single dose of up to 1,000 mg if body weight permits. 1, 2

Immediate Assessment and Transfusion Consideration

Before prescribing IV iron, assess for severe anemia-related symptoms and hemodynamic stability:

• If the patient has severe anemia-related symptoms (tachycardia, tachypnea, postural hypotension, chest pain) or hemodynamic instability, transfuse red blood cells immediately to maintain hemoglobin 8-10 g/dL as needed for symptom prevention 3
• If the patient is asymptomatic and hemodynamically stable without acute coronary syndrome, transfusion goal is to maintain hemoglobin 7-9 g/dL 3
• IV iron can be initiated concurrently or after stabilization, as it provides more gradual correction over 4-8 weeks 1, 4

Confirm Iron Deficiency Before Treatment

Check iron studies (serum ferritin, transferrin saturation, and complete blood count) to confirm iron deficiency anemia 1, 4:

• Absolute iron deficiency: ferritin <100 ng/mL (or <30 ng/mL without inflammation) 3, 1
• Functional iron deficiency: ferritin 100-800 ng/mL with transferrin saturation <20% 3, 1
• In patients with inflammation, ferritin up to 100 ng/mL may still indicate iron deficiency 1, 4

Specific Dosing Regimens

For Patients ≥50 kg Body Weight:

Standard regimen: 750 mg IV iron on day 1, repeat 750 mg at least 7 days later (total 1,500 mg per course) 2

Alternative single-dose regimen: 1,000 mg IV iron as a single dose (maximum 15 mg/kg, up to 1,000 mg) 2

For Patients <50 kg Body Weight:

15 mg/kg body weight IV iron in two doses separated by at least 7 days 2

Weight-Based Dosing for Severe Anemia (Hb 7-10 g/dL):

• Body weight <70 kg: 1,500 mg total iron 1
• Body weight ≥70 kg: 2,000 mg total iron 1

Administration Methods

Choose between two administration routes 2:

1. Undiluted slow IV push: Administer at approximately 100 mg (2 mL) per minute. For 1,000 mg doses, push over 15 minutes 2

2. IV infusion: Dilute up to 1,000 mg in no more than 250 mL sterile 0.9% sodium chloride (concentration ≥2 mg iron/mL), infuse over at least 15 minutes 2

Monitor the patient for at least 30 minutes after administration for hypersensitivity reactions 2. Ensure personnel and therapies for treating anaphylaxis are immediately available 2.

Special Considerations by Clinical Context

Cancer Patients on Chemotherapy:

• Administer 1,000 mg iron as single or multiple doses according to product label 3
• If receiving cardiotoxic chemotherapy, give IV iron before or after (not same day) or at end of treatment cycle 3

Chronic Kidney Disease Patients:

• Maintain transferrin saturation ≥20% and ferritin ≥100 ng/mL 3
• Hemodialysis patients require ongoing IV iron supplementation 3

Inflammatory Bowel Disease:

• IV iron is first-line for clinically active disease, hemoglobin <100 g/L, or oral iron intolerance 1

Heart Failure Patients:

• Follow specific weight and hemoglobin-based dosing protocols with maintenance doses at 12,24, and 36 weeks if ferritin <100 ng/mL 2

Monitoring Response

Recheck complete blood count and iron parameters 4-8 weeks after the last infusion 1, 4:

• Expected response: hemoglobin increase of 1-2 g/dL within 4-8 weeks 1, 4
• Do not check iron parameters too early (within 2 weeks), as circulating iron interferes with assays 1

Initiate maintenance therapy when 1:

• Serum ferritin drops below 100 ng/mL, or
• Hemoglobin falls below 12 g/dL (women) or 13 g/dL (men)

Critical Safety Precautions

Avoid extravasation, as brown discoloration may be long-lasting. If extravasation occurs, discontinue administration at that site 2

Check serum phosphate levels before repeat courses, especially if repeat treatment needed within 3 months, as ferric carboxymaltose can cause severe hypophosphatemia in 50-74% of patients 2, 5

Withhold IV iron during acute infection but not during chronic inflammation 1, 6

Contraindicated in patients with history of hypersensitivity to the specific IV iron formulation 2

The risk of serious hypersensitivity reactions with modern IV iron formulations is <1%, significantly lower than older preparations 5, 4. However, anaphylaxis can be life-threatening, so appropriate monitoring and emergency preparedness are mandatory 2.