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Ferrous Sulfate

Q: What are the absolute contraindications to the use of ferrous sulfate?

Contraindications to enteral iron preparations include: Hemolytic anemia—the condition is not caused by iron deficiency.Severe liver and kidney disease.Inflammatory and ulcerative GI lesions—peptic ulcer disease, ulcerative colitis, chronic inflammations due to the risk of mucosal irritation.

Ferrosi sulfas

For medical students2 min readUpdated 2026-10-10

Ferrous sulfate is a standard medication from the group of agents affecting the blood system. It serves as a source of ferrous iron required for hemoglobin synthesis and is used to treat iron deficiency states.

Pharmacological groupAgents affecting the blood system

Active substanceDivalent ionized iron (Fe2+)

Dosage formPowder

Dosage0.3–0.5 g orally

Pharmacodynamics and Absorption Characteristics

The active substance of the drug is ferrous sulfate heptahydrate ($FeSO_4 \cdot 7H_2O$). Its primary pharmacological feature is that it contains ferrous ionized iron ($Fe^{2+}$). This specific valence state is critical for absorption: ferrous iron ($Fe^{2+}$) has a significantly higher absorption rate in the gastrointestinal tract compared to ferric iron ($Fe^{3+}$).

Despite the high bioavailability of the ion itself, Ferrosi sulfas is rarely used as monotherapy in modern clinical practice. To achieve maximum therapeutic efficacy, it is included in combination drug formulations.

Combination Products (Absorption Modification)

To enhance therapy efficacy and improve absorption, ferrous sulfate is combined with special adjuvants. Depending on the additive, several classic combinations are distinguished:

With ascorbic acid (e.g., Ferroplex). Ascorbic acid acts as a reducing antioxidant. It prevents iron oxidation by reducing ferric iron ($Fe^{3+}$) back to ferrous iron ($Fe^{2+}$), which is absorbed much better by the intestinal mucosa.
With surfactants (e.g., Conferon). Sodium docusate is added to the formulation. This surfactant lowers surface tension, facilitating contact between iron ions and the mucosa and promoting their absorption.
With mucoprotease and ascorbic acid (e.g., Tardyferon). The addition of the enzyme mucoprotease further increases the bioavailability of iron ions in the GI tract.

Extended-Release Formulations

To maintain a stable iron concentration in the blood and reduce gastrointestinal irritation, modified-release formulations have been developed.

A prime example is Ferro-Gradumet. In this formulation, ferrous sulfate is integrated into a special polymer matrix (gradumet sponge). This structure ensures a gradual, controlled release of the active substance and its uniform absorption over several hours.

Indications and Place in Anemia Therapy

Ferrous sulfate preparations are strictly indicated for hypochromic (iron deficiency) anemias—conditions characterized by decreased hemoglobin synthesis due to a lack of building blocks.

Important for differential therapy: Ferrosi sulfas is completely ineffective and not used in hyperchromic anemias (particularly megaloblastic anemias). These anemias are characterized by an increased color index and excessive hemoglobin saturation of erythrocytes due to impaired cell division.

In $B_{12}$-deficiency anemia, the drug of choice is Cyanocobalamin.
In folate-deficiency states, Folic acid is prescribed.
In anemia of chronic disease or renal failure, Erythropoietin is used.

Prescription Example

The drug is available as a powder for oral administration. The standard single dose is 0.3–0.5 g.

Example of a prescription: ```latin Rp.: Ferrosi sulfatis 0.3 D.t.d. N. 20 S. Take 1 powder orally 3 times a day. ```

Mnemonic

"Ferrous is for absorption": iron must be in the $Fe^{2+}$ state to be efficiently absorbed in the GI tract. Ascorbic acid "saves" the iron by preventing its oxidation into the ferric ($Fe^{3+}$) form.

Frequently asked questions

What gastrointestinal side effects are characteristic of ferrous sulfate?

Gastrointestinal adverse reactions associated with iron preparations include:

Dyspeptic disorders—anorexia, nausea, vomiting, abdominal pain, metallic taste in the mouth.
Constipation—iron binds to hydrogen sulfide (which stimulates peristalsis), reducing bowel motility.
Diarrhea—occurs in approximately 20% of patients and requires symptomatic therapy.
Gastric irritation—nausea and epigastric discomfort, which can be minimized by taking the drug with meals.

Which drugs should not be taken concomitantly with ferrous sulfate due to impaired absorption?

Due to decreased absorption, ferrous sulfate should not be taken simultaneously with enterosorbents, including activated charcoal, as they inhibit drug absorption through surface binding.

What are the absolute contraindications to the use of ferrous sulfate?

Contraindications to enteral iron preparations include:

Hemolytic anemia—the condition is not caused by iron deficiency.
Severe liver and kidney disease.
Inflammatory and ulcerative GI lesions—peptic ulcer disease, ulcerative colitis, chronic inflammations due to the risk of mucosal irritation.

Why is ferrous sulfate rarely prescribed as monotherapy?

To enhance bioavailability and improve absorption in the GI tract, it is more effective to combine it with adjuvants such as ascorbic acid, mucoprotease, or surfactants.

What role does ascorbic acid play in combination iron preparations?

It acts as a reducing agent, converting ferric iron ($Fe^{3+}$) into ferrous iron ($Fe^{2+}$), which has a significantly higher absorption rate.

Can megaloblastic anemia be treated with ferrous sulfate?

No. Megaloblastic anemias are hyperchromic; they involve impaired DNA synthesis rather than hemoglobin synthesis. The drugs of choice here are cyanocobalamin (vitamin B12) and folic acid.

How does the "gradumet" formulation work?

It is an inert polymer matrix impregnated with ferrous sulfate, which ensures the gradual release of iron ions in the GI tract over several hours.

Go deeper

Iron metabolism in the body: absorption, transport (transferrin), and storage (ferritin).
Pharmacokinetic differences between ferrous ($Fe^{2+}$) and ferric ($Fe^{3+}$) iron.
Differential diagnosis of hypochromic, normochromic, and hyperchromic anemias.
Pharmacology of erythropoiesis stimulators: cyanocobalamin, folic acid, erythropoietin.
Drug-drug and drug-food interactions of iron preparations within the GI lumen.