Injectafer
Injectafer
Generic Name
Injectafer
Mechanism
- Polysaccharide‑bound ferric complex: Injectafer consists of ferric iron chelated to a carboxymaltose polymer, creating a macromolecule that is resistant to premature breakdown.
- Controlled release: The polymer matrix protects iron from immediate interaction with hemoglobin and prevents free iron from catalyzing oxidative damage.
- Targeted tissue delivery: After systemic circulation, the complex is taken up by macrophages of the reticuloendothelial system; iron is then released intracellularly and incorporated into transferrin for delivery to erythroid precursors.
- Rapid erythropoiesis: By directly supplying bioavailable iron, Injectafer accelerates red blood cell production, increasing hemoglobin and ferritin levels in a clinically significant time frame.
Pharmacokinetics
| Parameter | Typical Value (IV) | Notes |
| Volume of distribution (Vd) | ~0.5–0.7 L/kg | Limited extravasation due to large molecular size |
| Half‑life | 3–5 days (iron release phase) | Full elimination of iron occurs over 2–4 weeks |
| Clearance | ~3 mL/min/1.73 m² (renal component) | Majority excreted via hepatobiliary and macrophage recycling |
| Metabolism | None – iron is released and incorporated into native pathways | No hepatic metabolism; no drug–drug interaction via CYP450 |
| Protein Binding | >90 % bound to transferrin after release | Maintains iron in soluble, non‑toxic state |
Indications
- Iron‑deficiency anemia (IDA) in adults, adolescents, and children ≥12 y; when oral iron is ineffective, contraindicated, or poorly tolerated.
- Chronic kidney disease‑associated anemia requiring rapid iron repletion pre‑ESRD.
- Post‑partum hemorrhage and heavy menstrual bleeding in women; when oral iron is inadequate.
- Chemotherapy‑related anemia where high iron loads are required.
- Pre‑operative preparation for elective surgery to correct iron stores.
- Pregnancy‑related anemia in the second and third trimester when oral therapy is insufficient.
Contraindications
- Absolute: Active hypersensitivity to any component (including carbohydrate backbone), documented iron overload (e.g., hemochromatosis).
- Relative: Severe hepatic impairment (ALT > 5× ULN), active systemic infection or sepsis (risk of iron‑enhanced bacterial growth).
- Warnings:
- *Allergy*: Potential infusion reactions (rash, urticaria, anaphylaxis); monitoring during first 30 min.
- *Hypotension*: Rapid infusion can induce vasodilation; slow administration recommended.
- *Iron overload*: Excessive dosing may lead to iron deposition; monitor ferritin/TSAT.
- *Hypersensitivity to iron*: Previous severe reactions preclude use.
Dosing
Adults and Adolescents
• Initial dose: 20–50 mg elemental iron per kg (maximum 1 g) given as a 1‑hour infusion.
• Maintenance: Second dose within 1–2 weeks if ferritin < 100 ng/mL or TSAT < 20 %.
• Total monthly iron: ≤ 800 mg elemental iron; adjust based on lab response.
Children (≤12 y)
• Dose: 20 mg/kg elemental iron (max 400 mg) once per infusion.
• Follow‑up: Re‑evaluate ferritin/TSAT after 2–4 weeks.
Administration Guidelines
• Infuse over 30–60 min, preferably 1 h for 1 g dose; extend to 2 h if infusion‑related reaction risk.
• Monitor vitals and symptomatology during infusion and for 30 min post‑infusion.
• Use standard IV access; avoid infusion through high‑pressure lines.
Adverse Effects
| Common (≥1 %) | Serious (≤0.5 %) |
| Infusion site discomfort | Infusion‑related anaphylaxis |
| Flushing, headache | Hypotension or arrhythmias |
| Nausea, vomiting | Hepatotoxicity (rare) |
| Mild erythema | Iron overload syndrome (transient) |
Immediate Infusion Reactions
— Rash, pruritus, dizziness, bronchospasm.
Late‑onset Side Effects
— Hyperferritinemia, arthralgias (if ferritin > 800 ng/mL).
Monitor for signs of systemic iron deposition (e.g., cirrhosis, cardiomyopathy) in patients requiring repeated dosing.
Monitoring
| Parameter | Target | Frequency |
| Hemoglobin | 12–14 g/dL (women) / 13–15 g/dL (men) | Baseline, 4 wk, 8 wk |
| Serum ferritin | > 100 ng/mL (optimal) | Baseline, 4 wk, 12 wk |
| Transferrin saturation (TSAT) | 20–30 % | Baseline, 4 wk |
| Liver enzymes | ALT/AST ≤ 2× ULN | Baseline, 4 wk, 12 wk |
| Serum iron | 50–80 µg/dL | Baseline, 4 wk |
| Adverse reaction documentation | – | During infusion + 30 min post‑infusion |
Special Considerations
• For patients with chronic kidney disease, limit intravenous iron to 200–250 mg in a 4‑wk period and monitor for worsening anemia or iron overload.
• In pregnancy, monitor fetal status during repeat infusions; adjust dose accordingly.
Clinical Pearls
- Single‑Dose Feasibility: Injectafer can replenish > 300 mg elemental iron in a single 30‑minute infusion, reducing clinic visits by up to 75 % versus oral iron.
- Safety First: While first‑dose reactions are reported in 3–5 % of patients, they are usually mild; pre‑medication with antihistamines is optional and not routinely required.
- Iron Load Calculation: Use elemental iron dosing (20 mg/kg) rather than nominal iron content to avoid overdosing in patients with low iron‐requirements.
- Pregnancy Use: Evidence supports continued use of IV iron beyond second trimester; check ACOG guidelines before high‑dose therapy.
- Interpreting Ferritin: In acute inflammation, ferritin may be elevated; use TSAT and soluble transferrin receptor (sTfR) to discern true iron status.
- Drug Interaction: No pharmacokinetic interaction with antidiabetic, antihypertensive, or immunosuppressive agents; however, concurrent use of high‑dose corticosteroids may alter iron metabolism.
- Cost‑Benefit: Though pricier, the reduced need for oral iron supplements and lower risk of gastrointestinal side effects can lower overall treatment costs in severe IDA.
--
• *Disclaimer:* The data above are synthesized from available references on IV iron therapy and may not represent a real product. Always consult drug monographs, label information, and institutional guidelines before use.