Iron deficiency anemia is the most prevalent anemia, affecting 5% of the world’s adult population. Intravenous iron is administered in patients with diseases of the digestive tract that prevent digestive absorption. The indication for intravenous iron should always be made by a hematologist, who will also determine the frequency and amount of doses.
Prevalence of Iron Deficiency Anemia
Of all the types of anemia, iron deficiency anemia is the most prevalent, affecting 5% of the world’s adult population. This prevalence increases with age, so that, in the case of men, it stands at 2% for the age range between 18 and 50 years, increasing to almost 30% for those over 85 years of age. In the case of women, the prevalence is around 20% for the age range 18 to 50 years, increasing to 80% for those over 85 years of age. Among the most frequent causes are physiological menstrual losses in young women and chronic bleeding of gastrointestinal origin in patients over 55 years of age.
Importance of iron for the body and how it is metabolized
Iron is crucial for aerobic cell metabolism, cell growth and proliferation, development of the immune or defense system, as well as oxygen transport and storage. Approximately 65% of the iron in the body is found in hemoglobin, the protein that stains red blood cells red and is responsible for transporting oxygen to the different tissues. Another 10% is bound to other proteins such as myoglobin located in the muscles and the rest as a deposit in the liver in the form of ferritin.
Where is iron absorbed from the diet?
It should be taken into account that iron from the diet is absorbed in the distal part of the duodenum or first part of the jejunum and that this absorption is very limited, between 1-2 mg/day, which is, at most, 10-15% of all the iron that can be ingested during the day from the diet. This means that the integrity of the mucosa of this portion of the small intestine must be optimal for iron uptake to be facilitated.
If iron absorption is digestive, what is the point of using intravenous iron?
The main route of treatment of iron deficiency anemia is its oral administration, in its various formulations: tablets, granules, liquid, etc. However, on some occasions, the direct use of intravenous iron is more effective and useful. This occurs in patients with diseases affecting the digestive tract, especially of inflammatory or infectious origin such as gastritis, duodenitis or chronic inflammatory bowel disease (Crohn’s disease or ulcerative colitis). Also other autoimmune processes that can affect the mucosa of the digestive tract or resective surgical interventions that decrease the uptake area of iron and other nutrients mean that treatments with conventional oral iron do not have an adequate bioavailability profile, precisely because of a defect in absorption, with intravenous iron being more direct.
Other times it is the patient’s own intolerance to the components of oral iron producing constipation, gastric pain or diarrhea that makes it necessary to use the intravenous iron formulation.
On the other hand, intravenous iron is very useful as an adjuvant to other treatments in the anemia of oncological patients or chronic renal insufficiency, in which recombinant erythropoietin is administered.
Administration and risks of intravenous iron
The administration of intravenous iron should be carried out in a day hospital or consultation room, under the supervision of the specialist. It is administered through a peripheral venous access for a period of time ranging, depending on its formulation, from 30 minutes to one hour. After the administration, and after taking the patient’s basic constants, such as blood pressure, temperature and heart rate, the patient can go home.
The dose adjustment will be carried out by the hematologist or specialist in charge, depending on the response achieved, and can be done 1, 2 or 3 times a week for a period of 1 or 2 months.
This type of treatment is generally very well tolerated. The current provisions minimize the occurrence of side effects as much as possible. However, like any drug, it is not exempt from producing some adverse phenomenon of allergic or anaphylactoid origin such as: skin rash, fever, small hematoma at the puncture site or, very rarely, a frank bronchospasm crisis, as an established anaphylactic reaction.
As an anecdotal fact we can say that until 35-40 years ago, intravenous or parenteral iron was administered intramuscularly and this produced a permanent and unsightly tattoo at the puncture site, which is why this form of administration ceased to be used.