Antianaemic (iron)
Iron (ferrous sulfate) is a supplement used to treat and prevent iron deficiency anaemia. Absorption is limited (about 10-20% of the dose) and improves when taken on an empty stomach and with vitamin C. Accidental iron overdose is dangerous in children — keep out of reach.
Also known as: sulfato ferroso, ferrous sulfate, Ferrograd
Iron + calcium: calcium inhibits oral iron absorption.
Calcium reduces the absorption of non-haem iron in the gastrointestinal tract, both by competing for shared transporters and by forming complexes in the lumen. In patients with iron-deficiency anaemia taking iron supplements and, simultaneously, calcium supplements (common in women and older people), iron absorption can be impaired and delay correction of the anaemia. Separate the doses by at least 2 hours (e.g., iron at breakfast and calcium at dinner), and consider vitamin C (which enhances iron absorption) with the iron dose.
Calcium + iron: calcium inhibits oral iron absorption. Separate administration by 2 h.
Calcium competes with iron for intestinal transport.
Haematological response and adherence.
Persistent iron-deficiency anaemia.
Separate iron and calcium dosing by at least 2 hours.
DailyMed (FDA) — approved Iron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4e88a847-397b-4ddb-83d7-42c9b963a0b7 ; approved Calcium carbonate label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=348d3dfa-6a52-4583-96e3-83c4bf2df45b — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Omeprazole may reduce the absorption of oral iron, particularly non-heme iron.
Non-haem iron absorption (present in oral supplements) depends on acidic gastric pH, which keeps iron in the more absorbable ferrous form; omeprazole, by suppressing acid secretion, can reduce absorption and the efficacy of supplementation in patients with iron deficiency anaemia. In patients on a PPI with an unsatisfactory response to oral iron, consider increasing the dose, separating administrations, preferring haem iron or alternate-day dosing, and assess the need for intravenous iron.
Iron + omeprazole: raised pH reduces non-haem iron absorption. Monitor the response to supplementation and consider parenteral iron if needed.
Gastric acid suppression by the PPI impairs the reduction of Fe3+ to Fe2+, essential for duodenal iron absorption.
Monitor the therapeutic response of iron-deficiency anaemia.
Persistent iron-deficiency anaemia despite treatment.
Consider monitoring the response to iron (haemoglobin, ferritin); separate administration times.
DailyMed (FDA) — approved Iron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=73d1f079-d8eb-44f4-b33d-05fb25b80c8f ; approved Omeprazole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6ea9a6f3-b756-4cdf-b3db-f666a2c17d66 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Iron + zinc: they compete for intestinal absorption.
Iron and zinc share common intestinal transporters (e.g., DMT1, divalent metal transporters) and compete with each other for absorption when given simultaneously, especially at high doses. In patients taking combined iron and zinc supplementation (common in multiple deficiencies, pregnancy or malabsorption), absorption of both can decrease. Separate the doses (e.g., iron at breakfast and zinc at dinner) or give them at different times of day; taking them with food may reduce competition but also decreases absorption of both.
Iron + zinc: compete for intestinal absorption. Separate the doses.
Iron and zinc share intestinal transport mechanisms, reducing absorption of both when taken together.
Response to supplementation.
Persistent deficiency despite supplementation.
Separate dosing by at least 2 hours.
DailyMed (FDA) — approved Iron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4e88a847-397b-4ddb-83d7-42c9b963a0b7 ; approved Zinc (zinc sulfate) label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2bd646d2-2a2a-4376-8da0-c7f08b0511ac — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Iron + vitamin C: vitamin C increases oral iron absorption.
Ascorbic acid (vitamin C) reduces ferric iron (Fe³⁺) to ferrous (Fe²⁺) in the intestinal lumen and keeps it soluble, increasing absorption of non-haem iron — the Prontuário Terapêutico records that 30 mg of vitamin C enhance the absorption of 200 mg of iron. This is a clinically favourable interaction, often used to improve the response to iron supplementation in iron-deficiency anaemia; it poses no risk at usual doses. Take them together (or with citrus juice) to gain the benefit, while avoiding simultaneous intake with calcium, tea or coffee, which reduce iron absorption.
Iron + vitamin C: vitamin C increases oral iron absorption — a useful, not harmful, association.
Ascorbic acid reduces ferric to ferrous iron and forms soluble complexes, improving intestinal absorption.
Ferritin and haemoglobin.
Signs of iron overload (rare at usual doses).
Favourable combination: may allow a lower iron dose; watch for overload in at-risk patients.
DailyMed (FDA) — approved Iron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4e88a847-397b-4ddb-83d7-42c9b963a0b7 ; approved Ascorbic acid (vitamin C) label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1606e29f-0e80-4069-b688-daab9cbff20a — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Iron markedly reduces ciprofloxacin absorption through chelation.
Iron salts (ferrous, ferrous fumarate, etc.) release divalent cations that chelate ciprofloxacin in the gastrointestinal tract, reducing its oral bioavailability and potentially compromising antibacterial treatment. The ciprofloxacin label recommends administering the antibiotic 2 hours before or 6 hours after iron supplements (the same applies to antacids, calcium and zinc). This precaution is especially relevant in anaemic patients taking iron supplements during an antibiotic — check the schedules at prescription.
Ciprofloxacin + iron: iron cations chelate ciprofloxacin and reduce absorption. Administer 2 hours before or 6 hours after iron.
Fe2+/Fe3+ cations chelate the fluoroquinolone in the GI tract, reducing its bioavailability.
Monitor antibiotic efficacy (signs of persistent infection).
Therapeutic failure of ciprofloxacin; unresolved infection.
Give ciprofloxacin at least 2 hours before or 4 hours after iron.
DailyMed (FDA) — approved Iron label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=73d1f079-d8eb-44f4-b33d-05fb25b80c8f ; approved Ciprofloxacin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c527d138-e32c-418f-9573-a3d8a796279f — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcium-rich meals decrease iron absorption, mainly non-heme iron.
Separate iron from calcium-rich meals (2 hours).
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Calcium in milk and dairy competes with iron for intestinal transport, reducing its absorption.
Avoid taking iron with milk, yoghurt or cheese; separate doses by 2 hours.
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Tannins in coffee and tea form insoluble complexes with iron and reduce its oral absorption.
Take iron at least 1 to 2 hours before or after coffee, tea or tannin-rich drinks.
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Iron may mask other causes of anaemia; iron deficiency should be confirmed before treatment.
Confirm iron deficiency (ferritin, transferrin saturation) before supplementing.
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Iron supplementation is contraindicated in iron overload (haemochromatosis) and non-iron-deficiency anaemias with overload.
Do not give iron in haemochromatosis or overload; confirm iron-deficiency diagnosis.
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Iron is an essential nutrient in pregnancy; supplementation is safe at recommended doses.
Can be used in all trimesters at recommended doses for prevention/treatment of iron deficiency.
Iron is excreted into breast milk in small amounts, with no relevant risk to the infant.
No specific additional contraception.
EMC-UK (MHRA) — approved Iron SmPC: https://www.medicines.org.uk/emc/product/102243/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Essential mineral supplement (ferrous sulfate) used for the treatment and prevention of iron-deficiency anaemia and for iron replacement in deficiency states (pregnancy, bleeding, malabsorption). Oral absorption is limited (about 10-20% of elemental iron in iron-depleted patients) and regulated by hepcidin; accidental overdose is an important cause of fatal poisoning in children — keep out of reach.
Iron is an essential component of haemoglobin (oxygen transport) and of numerous enzymes (cytochromes, myoglobin). Intestinal absorption is regulated by hepcidin: absorbed iron raises hepcidin, which in turn reduces absorption of subsequent doses (feedback mechanism). Excess iron is stored as ferritin and haemosiderin.
Oral absorption occurs mainly in the duodenum and proximal jejunum. In iron-depleted women, daily doses raise hepcidin and reduce fractional iron absorption by 35-45% (alternate-day dosing optimises absorption). Bioavailability is highest when fasting (30 minutes before meals). About 10-20 mg of elemental iron are absorbed per day with oral therapy.
Iron is not metabolised in the classic sense: absorbed iron binds to transferrin in plasma and is transported to the bone marrow (erythropoiesis) and storage sites. Absorption of an oral dose is inversely proportional to iron stores; taking with food, tea, coffee, milk or antacids reduces absorption, while vitamin C increases it.
No classical elimination half-life applies: circulating iron (bound to transferrin) is rapidly taken up by the bone marrow and storage sites, and excess is sequestered as ferritin/haemosiderin. Therapeutic response is assessed by the rise in haemoglobin (1-2 g/dL within 2-4 weeks) and normalisation of ferritin.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
