Introduction
- Oral iron usually provides a safe, cheap and effective means of restoring iron balance in a patient with iron deficiency.
General Principles
- Iron is not absorbed in the stomach and is absorbed best from the duodenum and proximal jejunum. Therefore, enteric coated or sustained release capsules, which release iron further down in the intestinal tract, are less efficient sources of iron.
- Iron salts should not be given with food because phosphates, phytates, and tannates in food bind the iron and impair its absorption. A number of factors can inhibit the absorption of iron salts, including the use of antacids, certain antibiotics (eg, quinolones, tetracycline), and the ingestion of iron along with cereals, dietary fiber, tea, coffee, eggs, or milk.
- Iron should be given two hours before, or four hours after, ingestion of antacids.
- Iron is best absorbed as the ferrous (Fe2+) salt in a mildly acidic medium. A 250 mg ascorbic acid tablet can be added at the time of iron administration to enhance the degree of iron absorption.
- The iron preparation used should be based upon cost and effectiveness with minimal side effects. The cheapest preparation is iron sulfate; each tablet contains 325 mg of iron salts, of which 65 mg is elemental iron.
- Gastrointestinal tract symptoms (eg, abdominal discomfort, nausea/vomiting, diarrhea/constipation) suffered by some patients seem to be directly related to the amount of elemental iron ingested. Thus, the reported low incidence of side effects for some preparations can be explained by their low elemental iron content.
- Patients with persistent gastric intolerance to oral iron tablets may tolerate ferrous sulfate elixir, which provides 44 mg of elemental iron per 5 mL. Patients can titrate the dose up or down to the level at which the gastrointestinal symptoms become acceptable.
Choice of preparation
The most appropriate oral iron therapy is use of a tablet containing ferrous salts, such as:
- Ferrous fumarate contains 106 mg elemental iron/tablet.
- Ferrous sulfate contains 65 mg elemental iron/tablet.
- Ferrous gluconate contains 28 to 36 mg iron/tablet.
Dose
The recommended daily dose for the treatment of iron deficiency in adults is in the range of 150 to 200 mg/day of elemental iron; there is no evidence that one iron preparation is more effective than another for this purpose. As an example, a single 325 mg ferrous sulfate tablet taken orally three times daily between meals provides 195 mg of elemental iron per day.
Expected response
An effective regimen for the treatment of uncomplicated iron deficiency should lead to the following responses:
- If pica is present, it will disappear almost as soon as oral iron therapy is begun, well before there are any changes in the peripheral blood.
- The patient will note an improved feeling of well-being within the first few days of treatment.
- In patients with moderate to severe anemia, a modest reticulocytosis will be seen, maximal in approximately 7 to 10 days. Patients with mild anemia may have little or no reticulocytosis.The hemoglobin concentration will rise slowly, usually beginning after about one to two weeks of treatment, and will rise approximately 2 g/dL over the ensuing three weeks. The hemoglobin deficit should be halved by about one month and should return to normal by 6 to 8 weeks.
Side effects
Approximately 10 to 20 percent of patients may complain of nausea, constipation, epigastric distress and/or vomiting after taking oral iron preparations. There are a number of treatment options for such patients:
- The patient may take an iron preparation containing a smaller dose of elemental iron (eg, switching from ferrous sulfate to ferrous gluconate), or may switch from a tablet to a liquid preparation, the dose of which (44 mg elemental iron per 5 mL) can be easily titrated by the patient.
- The patient may slowly increase the dose from one tablet per day to the recommended three times per day, as tolerated.
- The iron may be taken with meals, although this will decrease absorption somewhat.
Duration of treatment
There is disagreement as to how long to continue iron therapy:
- Some physicians stop treatment with iron when the hemoglobin level becomes normal, so that further blood loss will cause anemia and alert the patient and physician to the return of the problem which caused the iron deficiency in the first place.
- Others believe that it is wise to treat for at least six months after the hemoglobin has normalized, in order to replenish iron stores.
Failure to respond to oral iron therapy
On occasion, a patient may not respond to oral iron therapy. The potential causes for this situation include the following:
- Incorrect diagnosis (eg, thalassemia, myelodysplastic syndrome).
- Presence of a coexisting disease interfering with response (eg, anemia of chronic inflammation, renal failure).
- Patient is not taking the medication.
- Medication is not being absorbed for physical reasons (eg, enteric coated tablets, concomitant use of antacids).
- Iron (blood) loss or need is in excess of the amount ingested (eg, severe continuous GI bleeding, dialysis patient, idiopathic pulmonary hemosiderosis).
- The patient has malabsorption for iron.
Pregnancy
Treatment of iron deficiency in pregnancy is the same as that in nonpregnant, postpartum, premenopausal, and postmenopausal women; indications for the use of parenteral iron are also the same