C H A P T E R 4 9
Drugs used to treat anaemias
789
A
gent
for
sickle cell anaemia
People with sickle cell anaemia are treated with antibiot-
ics to help fight the infections that can occur when blood
flow is decreased to any area; with pain-relieving activi-
ties to help alleviate the pain associated with the anoxia
to tissues, which can range from heat applied to the area
to OTC pain medications to prescription opioids; and
now, for adults, with hydroxyurea (
Hydrea
)
.
Hydroxy
urea is a cytotoxic antineoplastic drug that is also used
to treat leukaemia, ovarian cancer and melanoma.
Therapeutic actions and indications
Hydroxyurea, taken for several months, increases the
amount of fetal haemoglobin produced in the bone
marrow and dilutes the formation of the abnormal
haemoglobin S in adults who have sickle cell anaemia.
This results in less clogging of small vessels and the
painful, anoxic effects associated with the RBC sickling
or stacking. See Table 49.3 for usual indications.
Pharmacokinetics
Given orally, hydroxyurea is absorbed well from the GI
tract, reaching peak levels in 1 to 4 hours. It is metabo-
lised in the liver and excreted in the urine with a half-life
of 3 to 4 hours. It is known to cross the placenta and to
enter breast milk.
Contraindications and cautions
Hydroxyurea is contraindicated with known allergy
to any component of the drug
to prevent hypersensi-
tivity reactions
and with severe anaemia or leucopenia
because it can cause further bone marrow suppres-
sion.
It should be used with caution in the presence of
impaired liver or renal function,
which could inter-
fere with metabolism and excretion of the drug
, and it
should only be used in pregnancy and breastfeeding if
the benefit to the mother clearly outweighs the poten-
tial risk to the fetus or baby
because this drug crosses
the placenta and enters breast milk and could cause
serious effects in the fetus or baby.
sounds; and FBC, haematocrit and iron levels,
to
determine the effectiveness of drug therapy.
Implementation with rationale
■
■
Confirm the nature of the megaloblastic anaemia
to
ensure that the proper drug regimen is being used.
■
■
Give both types of drugs in cases of pernicious
anaemia
to ensure therapeutic effectiveness.
■
■
Parenteral vitamin B
12
must be given intramuscularly
each day for 5 to 10 days and then once a month for
life
if used to treat pernicious anaemia.
■
■
Arrange for nutritional consultation
to ensure a
well-balanced diet.
■
■
Monitor for the possibility of hypersensitivity
reactions;
have life support equipment on standby
in case reactions occur.
■
■
Arrange for haematocrit readings before and
periodically during therapy
to monitor drug
effectiveness.
■
■
Provide comfort measures
to help the person
tolerate drug effects.
These include small, frequent
meals, access to bathroom facilities and analgesia
for muscle or nasal pain.
■
■
Provide thorough teaching, including the name
of the drug, dosage prescribed, measures to avoid
adverse effects, warning signs of problems, and
the need for periodic monitoring and evaluation,
to enhance knowledge about drug therapy and to
promote compliance with the drug regimen.
■
■
Offer support and encouragement
to help the person
deal with the diagnosis and the drug regimen.
Evaluation
■
■
Monitor response to the drug (alleviation of
anaemia).
■
■
Monitor for adverse effects (nasal irritation, pain at
injection site, nausea).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects
to watch for and specific measures to avoid
them; individual understands the importance of
continued follow-up).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
Prototype summary: Hydroxyurea
Indications:
Reduction of frequency of painful crisis
and need for blood transfusions in adult people
with sickle cell anaemia.
Actions:
Increases fetal haemoglobin production
in the bone marrow and dilutes the formation of
abnormal haemoglobin S.
Pharmacokinetics:
Route Onset
Peak
Duration
Oral
Varied
1–4 hours
18–20 hours
T
1/2
:
3 to 4 hours; metabolised in the liver and
excreted in urine.
Adverse effects:
Dizziness, headache, rash, erythema,
anorexia, nausea, vomiting, stomatitis, bone
marrow depression, cancer.
