Ferrous fumarate

Ferrous fumarate is an oral iron supplement used in the prevention and treatment of iron deficiency anemia (IDA). It contains iron in the ferrous (Fe²⁺) form, which is more readily absorbed in the gastrointestinal tract than ferric salts. Ferrous fumarate is distinguished by its high elemental iron content relative to other common iron salts, such as ferrous sulfate and ferrous gluconate. This makes it a convenient option for meeting daily iron requirements with fewer tablets.

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Pharmacological Classification

• Therapeutic Class: Hematinic, anti-anemic agent

• Pharmacologic Class: Oral iron supplement

• ATC Code: B03AA02

• Common Forms:

  • Tablet (e.g., 210 mg) → typically contains ~65 mg elemental iron

  • Tablet (e.g., 322 mg) → ~105 mg elemental iron

  • Oral suspension: concentrations vary by brand

  • Combination products: may include folic acid (especially for pregnancy)

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Mechanism of Action

Iron is essential for the formation of hemoglobin, the oxygen-carrying protein in red blood cells. Ferrous fumarate restores depleted iron stores and supports hemoglobin synthesis. The ferrous form (Fe²⁺) is absorbed more efficiently in the duodenum and upper jejunum compared to ferric (Fe³⁺) iron. Once absorbed, iron:

• Joins the transferrin transport system in the blood

• Is delivered to the bone marrow for erythropoiesis

• Is stored in tissues as ferritin or hemosiderin for future use

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Indications

Treatment of Iron Deficiency Anemia

• Due to poor dietary intake, blood loss (e.g., menstruation, peptic ulcer, GI bleeding), malabsorption (e.g., celiac disease), or increased physiological demand (e.g., pregnancy)

Prevention of Iron Deficiency

• In high-risk populations:

  • Pregnant women

  • Infants and children

  • Menstruating women

  • Post-bariatric surgery patients

  • Chronic kidney disease patients (in some cases)

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Dosage and Administration

Adults (Treatment)

• 100–200 mg elemental iron daily in 1–2 divided doses

• Example: One 210 mg tablet of ferrous fumarate (65 mg elemental iron) twice daily

Adults (Prevention)

• 30–60 mg elemental iron once daily

Pregnancy

• Prophylactic: 30–60 mg elemental iron/day

• Therapeutic: Up to 120 mg elemental iron/day

Children

• Dose based on elemental iron per body weight:

  • 3–6 mg/kg/day, divided into 1–2 doses

  • Available as syrup or chewable tablets in pediatric formulations

Administration Advice

• Preferably taken on an empty stomach for optimal absorption

• Can be taken with food to reduce gastrointestinal discomfort

• Avoid taking with milk, tea, coffee, calcium, or antacids

• May be taken with vitamin C or orange juice to enhance absorption

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Pharmacokinetics

• Absorption: Mainly in the duodenum and proximal jejunum, enhanced in iron-deficient states

• Onset: Reticulocyte count typically increases within 5–10 days

• Peak hematologic response: Usually within 2–4 weeks, full replenishment of iron stores may require 3–6 months

• Transport: Iron binds to transferrin in the plasma

• Storage: Stored as ferritin in liver, spleen, and bone marrow

• Excretion: Minimal – excess iron is excreted slowly via sloughing of intestinal cells

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Contraindications

• Hemochromatosis

• Hemosiderosis

• Hemolytic anemia (not iron-responsive)

• Known hypersensitivity to ferrous fumarate or other iron salts

• Unexplained anemia without diagnostic confirmation

• Repeated blood transfusions (risk of iron overload)

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Warnings and Precautions

• Risk of iron overload with prolonged or inappropriate use

• Caution in patients with:

  • Peptic ulcers

  • Ulcerative colitis

  • Crohn’s disease

• Accidental overdose in children can be fatal – essential to store securely

• Prolonged use may mask serious underlying conditions such as colorectal carcinoma

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Adverse Effects

Very Common (>10%)

• Gastrointestinal disturbances:

  • Constipation

  • Abdominal pain

  • Nausea

  • Diarrhea

  • Dark (black) stools – harmless but may mask GI bleeding

Common (1–10%)

• Vomiting

• Flatulence

• Heartburn

• Metallic taste

Rare (<1%)

• Hypersensitivity reactions

• Esophageal irritation (especially if not swallowed properly)

• Teeth staining (with liquid forms)

• Anaphylaxis – rare and usually seen with intravenous iron, not oral forms

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Drug Interactions

Drugs That Reduce Iron Absorption

• Antacids, proton pump inhibitors (PPIs), H2 blockers – reduce stomach acid necessary for solubilization

• Calcium and magnesium supplements – compete for absorption

• Tetracyclines, fluoroquinolones, levothyroxine, bisphosphonates – form insoluble complexes; separate by 2–4 hours

Drugs Affected by Iron

• Methyldopa, levodopa, penicillamine – chelation reduces bioavailability

• Cholestyramine – may bind iron in the gut

• ACE inhibitors – increased risk of GI irritation in some combinations

Food Interactions

• Iron absorption is reduced by dairy products, tea, coffee, whole grains (phytates)

• Enhanced by ascorbic acid (vitamin C)

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Monitoring Parameters

• Hemoglobin (Hb) and hematocrit (Hct)

• Serum ferritin – best indicator of iron stores

• Transferrin saturation (TSAT)

• Reticulocyte count (rises after 5–10 days of adequate therapy)

• Evaluate for GI tolerance, especially in elderly

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Pregnancy and Lactation

Pregnancy

• Widely used and considered safe during pregnancy

• Included in prenatal supplements in combination with folic acid

Lactation

• Considered safe – iron content in breast milk not significantly altered

• Can be continued during breastfeeding if deficiency persists

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Use in Special Populations

Elderly

• May experience more constipation – stool softeners or increased fluids may help

Pediatrics

• Use appropriate liquid preparations with accurate dosing tools

• Never exceed recommended doses – risk of iron toxicity

Renal Impairment

• No specific adjustment needed for oral iron, but monitor for GI accumulation or overload

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Patient Counseling Points

• Take before meals, unless GI upset occurs

• Do not crush or chew extended-release tablets

• Iron may cause black stools – this is normal

• Constipation is common – increase fluid and fiber intake

• Avoid tea, milk, and antacids around the time of administration

• Separate iron from interfering medications by 2–4 hours

• Store out of reach of children

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Comparison to Other Iron Salts

• Ferrous sulfate: Most commonly used; ~65 mg elemental iron per 200 mg

• Ferrous fumarate: Higher elemental iron (approximately 33%) → fewer tablets needed

• Ferrous gluconate: Lower elemental iron (~12%) → gentler on stomach, requires more tablets

Ferrous fumarate is often preferred when:

• Higher elemental iron content per dose is desired

• Patient adherence is a concern (fewer tablets per day)

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Brand Names

• Ferretts®

• Hemocyte®

• Feostat®

• Femiron®

• Ferocon®

• Pregaday® (ferrous fumarate + folic acid – pregnancy use)

• Generic formulations widely available