Parental iron preparation enumerate pharmacology

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I now have comprehensive data from Goodman & Gilman's, Katzung's, and Lippincott's. Here is the full enumerated pharmacology of parenteral iron preparations:

Parenteral Iron Preparations - Pharmacology

Overview

Parenteral iron is indicated when:

Oral iron is not tolerated or absorbed (malabsorption syndromes, inflammatory bowel disease, post-gastrectomy)
Rapid iron repletion is needed
Patient is on erythropoietin therapy (especially CKD/hemodialysis)
Ongoing blood loss cannot be managed with oral iron

The key principle: inorganic free ferric iron is highly toxic, so all preparations use a colloid of iron oxyhydroxide surrounded by a carbohydrate shell that slowly releases bioactive iron. This limits dose-dependent toxicity.

1. Iron Dextran

Structure: Ferric oxyhydroxide complexed with dextran polymers. Contains 50 mg elemental iron/mL. Molecular weight ~180 kDa. Available as low-MW (INFed) and high-MW (Dexferrum) forms.

Route: IV (preferred) or deep IM

Mechanism: After IV injection, cleared by reticuloendothelial cells. At doses <500 mg, plasma t1/2 is ~6 h. At doses ≥1 g, RES clearance is constant at 10-20 mg/h.

Dosing:

Single dose of 1000 mg, or multiple doses of 100 mg
Always give a 25 mg (0.5 mL) test dose first
IM: max 25 mg/day (infants <4.5 kg), 50 mg/day (children <9 kg), 100 mg/day (all others)

Adverse effects: Headache, fever, arthralgias, nausea/vomiting, back pain, flushing, urticaria, bronchospasm, anaphylaxis (risk highest with high-MW formulation)

Monitoring: Withhold if plasma ferritin rises above 800 µg/L. Observe patient for at least 1 hour after injection for hypersensitivity.

Note: High-MW iron dextran carries the greatest anaphylaxis risk among all parenteral iron preparations. Low-MW iron dextran is significantly safer.

2. Sodium Ferric Gluconate (Ferric Gluconate)

Structure: Molecular size ~295 kDa; osmolality 990 mOsm/L

Route: IV only

Indication: Iron deficiency in CKD patients on hemodialysis with supplemental EPO therapy

Mechanism: Unlike iron dextran (which requires macrophage processing over weeks), ~80% of ferric gluconate is delivered to transferrin within 24 hours - much faster bioavailability.

Dosing: Multiple doses of 125-250 mg; 125 mg administered over 1 hour during hemodialysis

Adverse effects: Significantly lower risk of serious anaphylaxis compared to iron dextran

Special note: Avoided in pregnancy - contains benzyl alcohol preservative (potential fetal risk)

3. Iron Sucrose

Structure: Polynuclear iron (III)-hydroxide complex in sucrose

Route: IV only (slow injection or infusion)

Indication: Iron deficiency in CKD patients (both dialysis and non-dialysis dependent)

Mechanism: After IV injection, the complex is taken up by the reticuloendothelial system, where it dissociates into iron and sucrose. Iron is then stored as ferritin or transferred to transferrin.

Dosing: Multiple doses of 100-300 mg; typically 100-200 mg/day within a 14-day period; total cumulative dose of 1000 mg

Adverse effects: Lower anaphylaxis risk than iron dextran (similar safety profile to ferric gluconate)

Pregnancy: Less preferred - requires multiple infusions rather than a single replacement dose

4. Ferumoxytol

Structure: Superparamagnetic iron oxide nanoparticle coated with carbohydrate (semisynthetic)

Route: IV infusion

Indication: Iron deficiency anemia in adults with CKD, or intolerance/unsatisfactory response to oral iron

Mechanism: The carbohydrate shell is removed in the reticuloendothelial system, releasing iron to be stored as ferritin or transferred to transferrin.

Dosing: Single dose 1020 mg; or two doses of 510 mg given 3-8 days apart; administered over at least 15 min (30 min for 1020 mg dose)

Adverse effects:

FDA Black Box Warning for potentially fatal allergic reactions
Interferes with MRI imaging (superparamagnetic properties) - MRI should be done before ferumoxytol or an alternative imaging modality used after dosing

Monitoring: Observe for signs of hypersensitivity for at least 30 minutes after infusion

5. Ferric Carboxymaltose

Structure: Ferric iron embedded within a carbohydrate (carboxymaltose) polymer colloid

Route: IV (slow IV push over 15 min)

Indication: Iron deficiency anemia with intolerance/unsatisfactory response to oral iron; non-dialysis-dependent CKD

Dosing:

Weight ≥50 kg: two doses of 750 mg, given ≥7 days apart
Weight <50 kg: two doses of 15 mg/kg, given ≥7 days apart

Advantage: Requires only 2 doses (more convenient than iron sucrose/ferric gluconate requiring multiple infusions)

6. Ferric Derisomaltose (Iron Isomaltoside)

Structure: Ferric iron complexed with isomaltoside (derisomaltose)

Route: IV

Indication: Iron deficiency anemia with intolerance/unsatisfactory response to oral iron; non-dialysis-dependent CKD

Dosing:

Weight ≥50 kg: single dose of 1000 mg (or up to 3 doses of 500 mg over 7 days)
Weight <50 kg: single dose of 20 mg/kg
Doses ≤500 mg can be given as slow IV bolus (250 mg/min); doses >1 g over at least 30 min

Advantage: Allows single large-dose replacement - particularly useful when a one-session repletion is desired

Summary Comparison Table

Preparation	Structure	Key Indication	Anaphylaxis Risk	Special Concerns
Iron dextran (low-MW)	Iron-dextran polymer	Broad (intolerance/malabsorption)	Moderate	Test dose mandatory
Iron dextran (high-MW)	Iron-dextran polymer	Being phased out	Highest	Avoid if possible
Ferric gluconate	Iron-gluconate complex	CKD + hemodialysis + EPO	Low	Avoid in pregnancy (benzyl alcohol)
Iron sucrose	Iron-sucrose complex	CKD	Low	Multiple infusions required
Ferumoxytol	Iron oxide nanoparticle	CKD / oral iron intolerance	Low-moderate	MRI interference; Black Box Warning
Ferric carboxymaltose	Iron-carbohydrate polymer	Oral intolerance / non-dialysis CKD	Low	Only 2 doses needed
Ferric derisomaltose	Iron-isomaltoside	Oral intolerance / non-dialysis CKD	Low	Single-dose repletion possible

Key Pharmacokinetic Principles

Bypasses GI regulatory mechanism - unlike oral iron, parenteral administration can deliver more iron than can be safely stored. This is why iron overload monitoring is mandatory.
Iron stores monitoring: Serum ferritin and transferrin saturation (serum iron / TIBC ratio) must be monitored regularly during chronic parenteral therapy.
Test dose: Required for iron dextran; a test dose (given over 5-30 min) is recommended for any parenteral iron formulation before a full dose.
RES processing: All preparations ultimately release iron through the reticuloendothelial system (macrophages), where iron is stored as ferritin then transferred to transferrin for erythropoiesis.

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, Table 45-6 and p. 930 | Katzung's Basic and Clinical Pharmacology 16e, p. 933 | Lippincott Illustrated Reviews Pharmacology, p. 1478

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