A Textbook of Clinical Pharmacology and Therapeutics

and is normally 54–80μmol/L. Transferrin saturation (i.e.
plasma iron divided by TIBC) is normally 20–50% and pro-
vides a useful index of iron status. In iron-deficiency states,
TIBC rises in addition to the fall in plasma iron, and when
transferrin saturation falls to less than 16%, erythropoiesis
starts to decline. The cause of iron deficiency is most often
multifactorial, e.g. poor diet combined with excessive
demands on stores (pregnancy, chronic blood loss, lactation),
reduced stores (premature birth) or defective absorption
(achlorhydria, surgery to the gastro-intestinal tract). Although
treatment of iron deficiency is straightforward, its cause
should be determined so that the underlying condition can be
treated. Iron-deficiency anaemia in men or post-menopausal
women is seldom due solely to dietary deficiency, and a thor-
ough search for other causes (notably colon cancer) should be
undertaken.

IRON PREPARATIONS

ORAL IRON

Most patients with iron deficiency respond to simple oral iron
preparations. Treatment is continued for 3–6 months after

haemoglobin concentrations enter the normal range, in order

to replace iron stores. Failure to respond may be due to:

• wrong diagnosis;


• non-compliance with therapy;


• continued blood loss;


• malabsorption (e.g. coeliac disease, post-gastrectomy).
  There are too many iron-containing preparations available,
  many containing vitamins as well as iron. None of these com-
  binations carries an advantage over iron salts alone, except for
  those containing folic acid, which are used prophylactically in
  pregnancy. Treatment should start with a simple preparation
  such as ferrous sulphate, ferrous fumarate or ferrous glu-
  conate. Examples of commonly available iron preparations are
  listed in Table 49.1.

Adverse effects

Gastro-intestinal side effects, including nausea, heartburn, con-

stipation or diarrhoea, are common. Patients with ulcerative

colitis and those with colostomies suffer particularly severely

from these side effects. No one preparation is universally better

tolerated than any other, but individual patients often find

that one salt suits them better than another. Ferrous sulphate is

least expensive, but if it is not tolerated it is worth trying an

organic salt, e.g. fumarate. Although iron is best absorbed in the

fasting state, gastric irritation is reduced if it is taken after food.

Accidental overdose with iron is not uncommon in young

children and can be extremely serious, with gastro-intestinal

haemorrage, cardiovascular collapse, hepatic and neurotoxicity.

Desferrioxamine (an iron-chelating agent) is administered to

treat it (Chapter 54).

IRON PREPARATIONS FOR CHILDREN

Sugar-free liquid preparations that do not stain the teeth

should be used in paediatrics (e.g. sodium iron edetate). The

dose is calculated in terms of the amount of elemental iron.

PARENTERAL IRON

Oral iron is effective, easily administered and cheap. Parenteral

iron (formulated with sorbitol and citric acid) is also effective,

but can cause anaphylactoid reactions and is expensive. The

rate of rise in haemoglobin concentration is no faster than after

oral iron, because the rate-limiting factor is the capacity of the

390 ANAEMIA AND OTHER HAEMATOLOGICAL DISORDERS

Ferritin in

liver cells

Other cell systems

(e.g. myoglobin,

cytochromes)

Iron absorption

from gut

Transferrin

Red cell

precursors in

bone marrow

Red cell breakdown

Iron resorption by

macrophages

Red cells in
circulation
Figure 49.1:Iron metabolism.

Table 49.1:Ferrous iron content and relative cost of available iron formulations

Iron formulation Ferrous iron content Approximate ratio of cost

in one unit dose for one unit dose

Ferrous sulphate 60 mg 1

Ferrous fumarate 65 mg 2

Ferrous gluconate 35 mg 2.6

Ferrous succinate 35 mg 3

Sodium ironedetate 27.5–55 mg 6

Polysaccharide iron complex 50–100 mg 11