C H A P T E R 4 9
Drugs used to treat anaemias
783
to haemoglobin or trapped in reticuloendothelial cells
for storage and eventual release and conversion into
a usable form of iron for RBC production. Oral iron
preparations are often used to help these people regain
a positive iron balance; these preparations need to be
supplemented with adequate dietary intake of iron.
They are indicated for the treatment of iron-deficiency
anaemias and may also be used as adjunctive therapy
in people receiving an erythropoiesis-stimulating drug.
The drug of choice depends on the prescriber’s personal
preference and experience, and often on what kinds of
samples are available to give the person. See Table 49.2
for usual indications.
Pharmacokinetics
Ferrous fumarate and ferrous sulfate are available for
oral administration. Iron polymaltose is a parenteral
form of iron given by the Z-track method.
Individuals should be switched to the oral form
if at all possible because of the pain associated with
intramuscular (IM) administration of iron. Iron pol-
ymaltose is given intravenously specifically for people
who are undergoing chronic haemodialysis or who are
in renal failure and not on dialysis but are receiving
supplemental erythropoietin therapy.
Iron is primarily absorbed from the small intestine
by an active transport system. It is transported in the
blood, bound to transferrin. Small amounts are lost
daily in the sweat, urine, sloughing of skin and mucosal
cells, and sloughing of intestinal cells, as well as in the
menstrual flow of women. Most of the oral drug that is
taken is lost in the faeces, but slowly some of the metal is
absorbed into the intestine and transported to the bone
marrow. It can take 2 to 3 weeks to see improvement
and up to 6 to 10 months for a return to a stable iron
level once a deficiency exists. It is used during pregnancy
and breastfeeding to help the mother meet the increased
demands for iron that occur at those times.
Contraindications and cautions
These drugs are contraindicated for people with known
allergy to any of these preparations
because severe
hypersensitivity reactions have been associated with the
parenteral form of iron
. They also are contraindicated in
the following conditions: haemochromatosis (excessive
iron); haemolytic anaemias,
which may increase serum
iron levels and cause toxicity
; normal iron balance
because the drug will not be absorbed and will just pass
through the body
; and peptic ulcer, colitis or regional
enteritis
because the drug can be directly irritating to
these tissues and can cause exacerbation of the diseases.
Adverse effects
The most common adverse effects associated with oral
iron are related to direct GI irritation; these include
GI upset, anorexia, nausea, vomiting, diarrhoea, dark
stools and constipation. With increasing serum levels,
iron can be directly toxic to the CNS, causing coma and
even death. Box 49.3 discusses iron toxicity and drugs
that are used to counteract this effect. Parenteral iron
is associated with severe anaphylactic reactions, local
irritation, staining of the tissues and phlebitis.
See the
Critical thinking scenario for additional information
about iron preparations and toxicity
.
Clinically important drug–drug interactions
Iron absorption decreases if iron preparations are taken
with antacids, tetracyclines or cimetidine; if these drugs
must be used, they should be spaced at least 2 hours apart.
Anti-infective response to ciprofloxacin, norfloxacin
or ofloxacin can decrease if these drugs are taken with
iron because of a decrease in absorption; they should
also be administered at least 2 hours apart. Increased
iron levels occur if iron preparations are taken with
A
B
D
C
FIGURE 49.4
Use of the Z-track, or zigzag, technique for injections.
A.
Normal skin and tissues.
B.
Move the skin to one side.
C.
Insert
the needle at a 90-degree angle and aspirate for blood.
D.
Withdraw
the needle, and allow the displaced tissue to return to normal
position, thereby keeping the solution from leaving the muscle tissue.
