Ferrous Sulfate
Ferrous sulfate
Generic Name
Ferrous sulfate
Mechanism
- Iron delivery: Provides elemental iron (Fe²⁺) that enters enterocytes via the divalent metal transporter 1 (DMT1).
- Intracellular utilization: Once inside enterocytes, iron is stored as ferritin or exported to the bloodstream by ferroportin.
- Hemoglobin synthesis: Circulating iron is bound to transferrin, delivered to bone‑marrow erythroid precursors, where it is incorporated into heme and ultimately hemoglobin.
This sequential process replenishes iron stores, increases red‑cell production, and raises hemoglobin concentration.
Pharmacokinetics
| Parameter | Typical Value | Notes |
| Absorption | Peak serum iron 1–2 h after oral dose | Competitive with other divalent cations; best taken on an empty stomach for maximal absorption |
| Bioavailability | ~10–35 % of elemental iron | Varies with dose, food, GI integrity |
| Half‑life | 40–80 min (circulating iron) | Rapid clearance; storage in ferritin prolongs effect |
| Distribution | Primarily extravascular | Distributed to bone marrow, liver, spleen |
| Elimination | Renal; ~1‑2 % of dose excreted in urine | Minor fecal loss |
Key Points: Food, calcium, coffee, and antacids inhibit absorption; vitamin C, citrus juices, and zinc tablets enhance it.
Indications
- Iron deficiency anemia (IDA) in pre‑ and post‑menopausal women, men, children, and pregnancy
- Recurrent iron deficiency from chronic blood loss (e.g., heavy menstrual bleeding, gastrointestinal bleeding)
- Post‑surgical or peri‑operative anemia management
- Iron repletion in conditions causing increased utilization (e.g., hemolytic anemias, neoplastic disease)
Contraindications
| Category | Precautions |
| Overdose | Not usable for iron overload; severe toxicities include metabolic acidosis, organ failure |
| Pseudomembranous colitis risk | High doses, especially in immunocompromised patients |
| Known hypersensitivity to ferrous sulfate or sulfates | Avoid |
| Pregnancy & lactation | Generally safe but use lower doses; discuss risk‑benefit with provider |
| Patients with hemochromatosis | Contraindicated; iron loading worsens disease |
| GI disease | Inflammatory bowel disease may increase absorption, heightening risk of toxicity |
*Warnings:* Gastrointestinal irritation, nausea, dyspepsia, constipation, and black stools are common. Monitor for signs of iron overload in chronic users.
Dosing
| Age | Dose | Frequency | Administration Tips |
| Adults (≥18 y) | 325 mg elemental Fe (equiv. to 65 mg ferrous sulfate) | 1–2 × daily | Take 30 min before meal; avoid dairy, tea, and supplements with high calcium or zinc |
| Children (6–12 y) | 5–10 mg elemental Fe/kg/day | Divided doses | Prefer aqueous suspension; ensure adequate daily iron requirement |
| Pregnant women (≥12 wk) | 27 mg elemental Fe/day | Once daily | Prefer lower dose to reduce GI side effects |
• Titration: Begin with low dose; increase based on tolerance and hemoglobin response.
• Compliance: Emphasize adherence; regular monitoring of CBC and ferritin.
Adverse Effects
Common (≤10 % incidence):
• Nausea, dyspepsia, epigastric discomfort
• Intermittent constipation or diarrhea
• Dark, tarry stools (benign pigment change)
• Metallic taste
Serious (≤1 % incidence):
• Severe GI bleeding or ulceration
• Acute iron toxicity (metabolic acidosis, multi‑organ failure) after ingestion > 10 mg/kg elemental iron
• Allergic reactions (rash, urticaria, anaphylaxis)
Monitoring for Toxicity: Watch for signs of hypoxia, decreased urine output, and signs of gastrointestinal perforation.
Monitoring
| Parameter | Target | Frequency | Rationale |
| Hemoglobin / Hematocrit | ↑ by ≥1–2 g/dL by 4–6 weeks | 2–4 weeks → monthly | Evaluate efficacy |
| Serum ferritin | ≥30 ng/mL (women), ≥50 ng/mL (men) | baseline, 3–6 weeks, then 3 months | Assess iron stores |
| Serum iron / TIBC | ↑ in 12–24 h after dose | baseline, 3–6 weeks | Check absorption |
| Serum creatinine / BUN | Stable | baseline, 3 months if chronic use | Renal safety |
| Liver enzymes | Normal | baseline, 3 months if >6 mo >300 mg/day | Check hepatic function |
Note: In patients with chronic illnesses, monitor iron parameters more frequently (e.g., every 4 weeks) until stable.
Clinical Pearls
- “Squeeze the Juice”: Take ferrous sulfate with a glass of vitamin‑C‑rich citrus juice to enhance absorption—particularly valuable for patients who are notoriously non‑compliant.
- “Time of Day Matters”: Administer the first dose 30 minutes before breakfast; subsequent doses at bedtime to minimize nausea.
- “Avoid the “Gold‑Dust”: Avoid concomitant ingestion of calcium supplements, antacids, or high‑protein meals within 2 h of dosing; they chelate iron and decrease absorption.
- “Black Stools Alert”: It is normal for stools to darken; however, sudden bright red bleeding warrants prompt evaluation for GI pathology.
- “Tailored Dosing for Children”: Use liquid formulations (e.g., ferrous sulfate suspension 3 mg/mL) for better taste masking and dose precision.
- “Monitor for Over‑Supplementation”: Even routine dosing can accumulate to toxic levels in patients with malabsorption disorders—review iron status every 3–6 months if on long‑term therapy.
- “Patient Education”: Emphasize adherence and report any abdominal pain or black vomiting—these may be early signs of acute iron poisoning.
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• *References:* Updated 2025 based on latest clinical pharmacology guidelines and peer‑reviewed literature.