Haematinics and Drugs for Anaemia
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Direct answer
Oral iron salts remain first-line for iron deficiency anaemia: about 100-200 mg of elemental iron daily, though alternate-day dosing is now preferred because it avoids hepcidin spikes and improves absorption. Ferrous sulphate 325 mg carries roughly 65 mg of elemental iron. Parenteral iron — iron sucrose 200 mg or ferric carboxymaltose up to 1000 mg in one sitting — is reserved for intolerance, malabsorption, ongoing blood loss or late-pregnancy severity. Folic acid 5 mg and vitamin B12 (1000 micrograms orally or intramuscularly) treat megaloblastic anaemia, while erythropoiesis-stimulating agents correct renal anaemia. Judge response by reticulocytosis at 7-10 days and a haemoglobin rise of about 1 g/dL every 2-3 weeks.
What you must remember
- Elemental iron arithmetic: ferrous sulphate 325 mg ≈ 65 mg elemental, fumarate 200 mg ≈ 66 mg, gluconate 300 mg ≈ 35 mg — prescriptions are written in salt strength but dosed on elemental content.
- Pregnancy schedule (India): IFA tablet with 100 mg elemental iron + 500 micrograms folic acid daily from the second trimester; severely anaemic women get daily double dose; schoolgoing adolescents receive weekly IFA under the Weekly Iron and Folic acid Supplementation programme.
- Parenteral options: iron sucrose 200 mg IV on alternate days, ferric carboxymaltose 15 mg/kg (max 1000 mg) as a short infusion — the latter risks hypophosphataemia with repeated doses.
- Response markers: reticulocytosis by day 7, haemoglobin rise ~2 g/dL in 3 weeks; continue oral iron for 3 months after haemoglobin normalises to refill stores.
- Megaloblastic pair: folate 5 mg orally corrects the blood picture of B12 deficiency while neurological damage progresses — always exclude B12 deficiency first.
- Erythropoietin and newer agents: epoetin alfa and darbepoetin for CKD anaemia (watch hypertension and thrombosis); HIF-PHI oral agents like roxadustat are the newest additions.
- Iron poisoning: a toddler swallowing adult tablets shows gastric corrosion, high-anion-gap acidosis and shock; deferoxamine chelation with the characteristic vin-rose urine.
- NLEM anchor: iron+folic acid tablets and both parenteral irons appear in India's National List of Essential Medicines, 2022.
A worked case from the antenatal clinic
A third-trimester woman arrives with haemoglobin 7.8 g/dL, MCV 68 fL, low ferritin. Begin oral iron in the morning on an empty stomach with vitamin C-rich juice; tea within an hour of the dose chelates iron and is worth mentioning to her. Review at two weeks: reticulocytes should have risen even before haemoglobin moves. If she returns at 34 weeks still below 8 g/dL, or she cannot tolerate oral iron (black stools worry her, dyspepsia defeats her), give ferric carboxymaltose 1000 mg IV — it restores a gram of haemoglobin-raising iron in fifteen minutes of chair time. Transfusion is kept for haemoglobin under 7 g/dL or imminent delivery, because a single unit takes hours the pregnancy may not have. If instead the smear had shown macrocytosis with hypersegmented neutrophils, the sequence flips: check B12 before giving folate, since folate alone in an undiagnosed B12 deficiency can precipitate subacute combined degeneration.
Where students slip
The commonest error is quoting salt weight as dose — "ferrous sulphate 200 mg thrice daily" means only about 40 mg of iron per tablet, and examiners deliberately probe the elemental conversion. The second slip is forgetting why alternate-day dosing works: a large iron bolus induces liver hepcidin via BMP/SMAD signalling, which blocks ferroportin and slashes absorption of the very next dose — a viva favourite since it links pharmacology to iron physiology. Finally, candidates call erythropoietin a haematinic for all anaemias; it is worthless unless the marrow lacks the hormone, as in CKD, or is suppressed by cancer chemotherapy.
Frequently asked questions
Why is alternate-day oral iron now preferred over thrice-daily dosing?
Continuous high luminal iron raises hepcidin, which blocks ferroportin-mediated absorption for up to 48 hours; spacing doses exploits the hepcidin trough and increases the fraction absorbed per milligram given.
When is parenteral iron chosen over oral iron?
Intolerance despite formulation changes, malabsorption, ongoing blood loss exceeding gut absorption, and severe anaemia late in pregnancy where oral iron is too slow are the standard indications.
Which parenteral iron can be given as a 1000 mg single dose?
Ferric carboxymaltose, up to 15 mg/kg or 1000 mg per sitting; iron sucrose must be limited to 200 mg per visit because of infusion reactions.
Why must B12 deficiency be excluded before treating with folic acid?
Folate corrects the megaloblastic anaemia of B12 deficiency without halting — and sometimes unmasking progression of — neurological degeneration, so the haemoglobin improves while the cord damage advances.
How is treatment response to iron monitored?
Reticulocyte count at 7-10 days is the earliest marker; haemoglobin should rise about 1 g/dL every 2-3 weeks, and therapy continues three months beyond normalisation to replenish stores.