Introduction
Ferrous gluconate is an iron supplement used to treat and prevent iron deficiency anemia. It is an oral preparation containing a ferrous salt (iron in the +2 oxidation state) complexed with gluconic acid. As a second-generation iron preparation, it offers improved gastrointestinal tolerability compared to older iron salts while maintaining good bioavailability.
Mechanism of Action
Ferrous gluconate provides elemental iron, which is essential for hemoglobin synthesis and oxygen transport. After oral administration, the ferrous (Fe²⁺) iron is absorbed primarily in the duodenum and proximal jejunum via active transport mechanisms. Once absorbed, iron is incorporated into hemoglobin in developing red blood cells and stored as ferritin or hemosiderin. Iron serves as a cofactor for various enzymes involved in cellular respiration and metabolic processes.
Indications
- Treatment of iron deficiency anemia
- Prevention of iron deficiency in high-risk populations (pregnancy, chronic blood loss, malnutrition)
- Adjunct therapy in patients receiving erythropoietin
- Prophylaxis in blood donors with frequent donations
Dosage and Administration
Adults:- Treatment of iron deficiency: 325 mg (38 mg elemental iron) orally 2-4 times daily
- Maintenance/prophylaxis: 325 mg orally once daily
- 3-6 mg elemental iron/kg/day divided into 3-4 doses
- Renal impairment: No dosage adjustment required
- Hepatic impairment: Use with caution; monitor iron levels
- Pregnancy: 30-60 mg elemental iron daily recommended
- Geriatric: Standard dosing; monitor for constipation
- Take on empty stomach for maximum absorption (1 hour before or 2 hours after meals)
- If gastrointestinal upset occurs, may take with food (reduces absorption by 40-50%)
- Avoid taking with antacids, coffee, tea, or dairy products
- Separate administration from other medications by 2 hours
Pharmacokinetics
Absorption: 15-20% of administered dose absorbed primarily in duodenum and proximal jejunum; enhanced by acidic environment Distribution: Bound to transferrin and transported to bone marrow, liver, and spleen; crosses placenta Metabolism: Iron is incorporated into hemoglobin or stored as ferritin/hemosiderin Elimination: Minimal excretion; primarily lost through desquamation of intestinal mucosal cells, sweat, urine, and bile; women lose additional iron through menstruationContraindications
- Hemochromatosis or other iron overload disorders
- Hemolytic anemia
- Known hypersensitivity to ferrous gluconate or any component
- Repeated blood transfusions
- Aplastic anemia
Warnings and Precautions
- Accidental overdose: Iron poisoning is a leading cause of fatal poisoning in children under 6
- GI effects: May cause constipation, nausea, vomiting, abdominal pain
- Stool discoloration: May cause dark or black stools (not clinically significant)
- Dental effects: Liquid preparations may stain teeth
- Hemosiderosis: Risk with prolonged use in patients without deficiency
- Inflammatory conditions: May exacerbate symptoms in patients with ulcerative colitis or Crohn's disease
Drug Interactions
- Antacids, H2 blockers, PPIs: Decrease iron absorption
- Tetracyclines, fluoroquinolones: Form insoluble complexes; separate by 2-4 hours
- Levothyroxine: Decreased absorption; separate by 4 hours
- Cholestyramine: Decreased iron absorption
- Vitamin C: Enhances iron absorption
- Penicillamine: Decreased efficacy
- Chloramphenicol: Delayed iron utilization
Adverse Effects
Common (>10%):- Constipation
- Dark stools
- Nausea
- Epigastric pain
- Diarrhea
- Vomiting
- Heartburn
- Tooth discoloration (with liquid formulations)
- Allergic reactions
- Gastrointestinal ulceration
- Hemosiderosis (with prolonged overdose)
Monitoring Parameters
- Hemoglobin/hematocrit at 2-4 week intervals until normalized
- Reticulocyte count (should increase within 3-10 days)
- Serum ferritin (to assess iron stores)
- Total iron-binding capacity (TIBC)
- Transferrin saturation
- Gastrointestinal symptoms
- Compliance and tolerance
Patient Education
- Take on empty stomach for best absorption unless causing stomach upset
- Do not crush or chew sustained-release formulations
- Liquid preparations should be diluted and taken through a straw to prevent tooth staining
- Expect darkening of stools (normal and not harmful)
- Keep out of reach of children - iron overdose can be fatal
- Report severe constipation, abdominal pain, or signs of allergic reaction
- Do not stop taking prematurely even if feeling better
- Store in original container away from moisture
References
1. Lopez A, Cacoub P, Macdougall IC, et al. Iron deficiency anaemia. Lancet. 2016;387(10021):907-916. 2. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372(19):1832-1843. 3. Tolkien Z, Stecher L, Mander AP, et al. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015;10(2):e0117383. 4. Pasricha SR, Drakesmith H, Black J, et al. Control of iron deficiency anemia in low- and middle-income countries. Blood. 2013;121(14):2607-2617. 5. FDA prescribing information for ferrous gluconate preparations. 6. World Health Organization. Guideline: Daily iron supplementation in adult women and adolescent girls. Geneva: World Health Organization; 2016. 7. Schrier SL. So you know how to treat iron deficiency anemia. Blood. 2015;126(17):1971.