Introduction
FeroSul (ferrous sulfate) is an oral iron supplement used for the prevention and treatment of iron deficiency and iron deficiency anemia. As one of the most commonly prescribed and readily available iron preparations, it provides elemental iron in the ferrous (Fe2+) form, which is more readily absorbed than ferric (Fe3+) iron formulations.
Mechanism of Action
FeroSul works by providing exogenous iron, which is essential for hemoglobin formation and oxygen transport. Iron is incorporated into hemoglobin in developing erythrocytes in the bone marrow and serves as a cofactor for various enzymes involved in cellular respiration and metabolic processes. The ferrous sulfate salt dissociates in the gastrointestinal tract, allowing for absorption of ferrous iron primarily in the duodenum and proximal jejunum.
Indications
- Treatment of iron deficiency anemia
- Prevention of iron deficiency in high-risk populations (pregnancy, chronic blood loss, malnutrition)
- Prophylaxis in patients with increased iron requirements
Dosage and Administration
Adults:- Treatment: 325 mg (65 mg elemental iron) orally 2-3 times daily
- Prophylaxis: 325 mg orally once daily
- 3-6 mg/kg/day of elemental iron divided into 3 doses
- Renal impairment: No dosage adjustment required
- Hepatic impairment: Use with caution; monitor iron levels
- Geriatric: Consider reduced dosage due to potential decreased gastrointestinal tolerance
- Take on an empty stomach for maximum absorption (1 hour before or 2 hours after meals)
- If gastrointestinal upset occurs, administer with food (though absorption may decrease by 30-50%)
- Avoid concomitant administration with antacids, calcium supplements, or dairy products
- May be taken with vitamin C (ascorbic acid) to enhance absorption
Pharmacokinetics
Absorption: Iron is absorbed primarily in the duodenum and upper jejunum via active transport and passive diffusion. Absorption ranges from 5-35% depending on iron stores, with increased absorption in iron-deficient states. Distribution: Iron distributes primarily to bone marrow (for hemoglobin synthesis) with storage in reticuloendothelial cells as ferritin and hemosiderin. Metabolism: Iron is incorporated into hemoglobin or stored in ferritin. It undergoes minimal hepatic metabolism. Elimination: Minimal renal excretion; primarily eliminated in feces via sloughing of intestinal mucosal cells and in sweat, skin cells, and urine. Menstrual losses contribute to iron elimination in women.Contraindications
- Hemochromatosis or hemosiderosis
- Hemolytic anemia
- Known hypersensitivity to ferrous sulfate or any component of the formulation
- Patients receiving repeated blood transfusions
Warnings and Precautions
Black Box Warning: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children.- May exacerbate gastrointestinal diseases (peptic ulcer disease, ulcerative colitis, regional enteritis)
- Use with caution in patients with pre-existing hepatic impairment
- Iron overload may occur in patients with hereditary hemochromatosis or thalassemia
- May cause false positive results in fecal occult blood tests
- Dental staining may occur with liquid formulations
Drug Interactions
- Antacids, calcium supplements, dairy products: Decreased iron absorption
- Tetracyclines, fluoroquinolones, bisphosphonates: Decreased absorption of these medications
- Levothyroxine: Decreased levothyroxine absorption
- Chloramphenicol: May delay iron clearance from plasma
- ACE inhibitors: May cause increased systemic iron availability
- Proton pump inhibitors, H2 antagonists: May decrease iron absorption by reducing gastric acidity
Adverse Effects
Common (>10%):- Gastrointestinal upset (nausea, epigastric pain)
- Constipation or diarrhea
- Darkened stools (benign effect)
- Heartburn
- Abdominal cramping
- Staining of teeth (liquid formulation)
- Allergic reactions
- Gastrointestinal ulceration
- Iron overload with chronic excessive use
Monitoring Parameters
- Hemoglobin/hematocrit levels (every 3 months until normalized, then periodically)
- Reticulocyte count (should increase within 3-10 days of initiation)
- Serum ferritin and transferrin saturation
- Complete blood count with indices (MCV, MCH, MCHC)
- Gastrointestinal tolerance
- Signs of iron overload in long-term therapy
Patient Education
- Take on an empty stomach for best absorption, but with food if gastrointestinal upset occurs
- Expect darkening of stools (harmless effect)
- Do not exceed recommended dosage
- Keep out of reach of children - iron overdose can be fatal
- Separate dosing from antacids, calcium supplements, dairy products, and tea by at least 2 hours
- Liquid formulations may stain teeth; use straw or rinse mouth after administration
- Report severe constipation, abdominal pain, or signs of allergic reaction
- Store in original container with child-resistant cap
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. Goddard AF, James MW, McIntyre AS, et al. Guidelines for the management of iron deficiency anaemia. Gut. 2011;60(10):1309-1316. 4. FDA Drug Safety Communication: Iron-containing products. U.S. Food and Drug Administration. 2018. 5. 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. 6. Schrier SL. So you know how to treat iron deficiency anemia. Blood. 2015;126(17):1971.