C H A P T E R 4 9
Drugs used to treat anaemias
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not only for the health of the RBCs, but also for the
formation and maintenance of the myelin sheath in the
central nervous system (CNS). It is found in the diet in
meats, seafood, eggs and cheese. Strict vegetarians who
eat nothing but vegetables may develop a vitamin B
12
deficiency. Such individuals with a dietary insufficiency
of vitamin B
12
typically respond to vitamin B
12
replace-
ment therapy to reverse their anaemia.
The most common cause of this deficiency, however,
is inability of the GI tract to absorb the needed amounts
of the vitamin. Gastric mucosal cells produce a sub-
stance called intrinsic factor, which is necessary for the
absorption of vitamin B
12
by the upper intestine.
Pernicious anaemia
occurs when the gastric mucosa
cannot produce intrinsic factor and vitamin B
12
cannot
be absorbed. The person with pernicious anaemia will
complain of fatigue and lethargy, and will also have
CNS effects because of damage to the myelin sheath.
Individuals will also complain of numbness, tingling,
and eventually lack of coordination and motor activity.
Pernicious anaemia was once a fatal disease, but it
is now treated with parenteral or nasal vitamin B
12
to
replace the amount that can no longer be absorbed.
Sickle cell anaemia
Sickle cell anaemia is a chronic haemolytic anaemia that
occurs almost exclusively in black people (“haemolytic”
means that the anaemia involves a lysing or destruction
of RBCs). It is characterised by a genetically inherited
haemoglobin S, which gives the RBCs a sickle-shaped
appearance. The person with sickle cell anaemia
produces fewer than normal RBCs, and the RBCs that
are produced are unable to carry oxygen efficiently. The
sickle-shaped RBCs can become lodged in tiny blood
vessels, where they stack up on one another and occlude
the vessel. This occlusion leads to anoxia and infarction
of the tissue in that area, which is characterised by severe
pain and an acute inflammatory reaction, the person
may even have ulcers on the extremities as a result of
such occlusions. Severe, acute episodes of sickling with
vessel occlusion may be associated with acute infec-
tions as well as the body’s reactions to the immune and
inflammatory responses. In the past, sickle cell anaemia
was treated only with pain medication and support for
the person. Now hydroxyurea has been found to be
effective in treating this disease in adults.
■■
RBCs are produced in the bone marrow in a
process called erythropoiesis, which is controlled
by the glycoprotein erythropoietin, produced in the
kidneys. The bone marrow uses iron, amino acids,
carbohydrates, folic acid and vitamin B
12
to produce
healthy, efficient RBCs.
KEY POINTS
■■
Anaemia is a state of too few RBCs or ineffective
RBCs. Anaemia can be caused by a lack of
erythropoietin or a lack of the components needed to
produce RBCs.
■■
Anaemia can be categorised as deficiency (iron-
deficiency anaemia), megaloblastic (folic acid or
vitamin B
12
deficiency) or haemolytic (sickle cell).
ERYTHROPOIESIS-STIMULATING AGENTS
Individuals who are no longer able to produce enough
erythropoietin in the kidneys may benefit from treat-
ment with exogenous erythropoietin (EPO), which is
available as the drugs epoetin alfa (
Eprex
), epoetin beta
(
NeoRecormon
), epoetin lambda (
Novicrit
[not availa-
ble in New Zealand]), darbepoetin alfa (
Aranesp
) and
methoxy polyethylene glycol-epoetin beta (
Mircera
).
When agents are used to stimulate the bone marrow
to make more RBCs, it is important to ensure that the
person has adequate levels of the components required
to make RBCs, including adequate iron. See Table 49.1
for additional information about each of these agents.
Box 49.1 highlights important considerations for differ-
ent age groups when this group of drugs and other drugs
used to treat anaemia are administered.
Therapeutic actions and indications
Epoetin alfa acts like the natural glycoprotein erythro
poietin to stimulate the production of RBCs in the bone
marrow (see Figure 49.2). This drug is indicated in the
treatment of anaemia associated with renal failure and
for people on dialysis; for anaemia associated with
AIDS therapy; and for anaemia associated with cancer
chemotherapy when the bone marrow is depressed and
the kidneys may be affected by the toxic drugs. It is not
approved to treat other anaemias and is not a replace-
ment for whole blood in the emergency treatment of
anaemia. See Table 49.1 for additional indications.
Safe medication administration
With any of these drugs, there is a risk of decreasing the
normal levels of erythropoietin if this drug is given to people
who have normal renal functioning and adequate levels of
erythropoietin (see Adverse effects for important safety
information related to medication administration). Negative
feedback occurs with the renal cells and less endogenous
erythropoietin is produced if exogenous erythropoietin is
given. Administration of this drug to an anaemic person
with normal renal function can actually cause a more severe
anaemia if the endogenous levels fall and no longer stimulate
RBC production.
