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P A R T 8
Drugs acting on the cardiovascular system
Therapeutic actions and indications
The antihaemophilic drugs replace clotting factors
that are either genetically missing or low in a particu
lar type of haemophilia. The drug of choice depends on
the particular haemophilia that is being treated. Anti
haemophilic factor is factor VIII, the clotting factor
that is missing in classic haemophilia (haemophilia A).
This agent and antihaemophilic factor recombinant (a
genetically engineered product that does not use human
blood) are used to correct or prevent bleeding episodes
or to allow necessary surgery.
Coagulation factor VIIa (
NovoSeven
[NZ]) and
factor IX complex are used for people with haemo
philia A or B (see Table 48.4 for usual indications for
each of these agents). Coagulation factor VIIa is a prepa
ration made from mouse, hamster and bovine proteins
that contains variable amounts of preformed clotting
factors (see Contraindications and cautions). Factor
IX complex contains plasma fractions of many of the
clotting factors and increases blood levels of factors II,
VII, IX and X. The drug of choice for any given person
is determined by his or her particular coagulation
abnormalities.
Pharmacokinetics
These agents replace normal clotting factors and are
processed as such by the body. They must be given intra
venously and are processed by the body in the same way
that naturally occurring clotting factors are processed
in the plasma, usually with a half-life of 24 to 36 hours.
Contraindications and cautions
Antihaemophilic factor is contraindicated in the presence
of known allergy to mouse proteins
to prevent hyper-
sensitivity reactions
. Factor IX is contraindicated in the
presence of liver disease with signs of intravascular coag
ulation or fibrinolysis
to prevent serious aggravation of
these disorders
. Coagulation factor VIIa is contraindi
cated with known allergies to mouse, hamster or bovine
products
to prevent hypersensitivity reactions
. These
drugs are not recommended for use during breast
feeding, and caution should be used during pregnancy
because of the potential for adverse effects on the baby
or fetus.
They should be used during pregnancy only if
the benefit to the mother clearly outweighs the potential
risk to the fetus. It is recommended that another method
of feeding the baby be used if these drugs are needed
during breastfeeding. Because these drugs are used to
prevent serious bleeding problems or to treat bleeding
episodes, there are few contraindications to their use.
Adverse effects
The most common adverse effects associated with anti
haemophilic agents involve risks associated with the
use of blood products (e.g. hepatitis, AIDS). Headache,
flushing, chills, fever and lethargy may occur as a
reaction to the injection of a foreign protein. Nausea
and vomiting may also occur, as may stinging, itching
and burning at the site of the injection.
Prototype summary: Antihaemophilic factor
Indications:
Treatment of classic haemophilia to
provide temporary replacement of clotting factors
to correct or prevent bleeding episodes or to allow
necessary surgery.
Actions:
Normal plasma protein that is needed for
the transformation of prothrombin to thrombin,
the final step in the clotting pathway.
Pharmacokinetics:
Route Onset
Peak
Duration
IV Immediate Unknown Unknown
T
1/2
:
12 hours; cleared from the body by normal
protein metabolism.
Adverse effects:
Allergic reaction, stinging at
injection site, headache, rash, chills, nausea,
hepatitis, AIDS (risks associated with the use of
blood products).
Care considerations for
people receiving antihaemophilic agents
Assessment: History and examination
■
■
Assess for the following conditions,
which could
be cautions or contraindications to use of the
drug
: any known allergies to these drugs or to
mouse proteins with antihaemophilic factor; liver
disease.
■
■
Assess for baseline status before beginning therapy
to determine any potential adverse effects.
■
■
Assess the following: body temperature; skin
colour, lesions and temperature; affect, orientation
and reflexes; pulse, blood pressure and perfusion;
respirations and adventitious sounds; clotting
studies; and hepatic function tests.
Implementation with rationale
■
■
Administer by the IV route only
to ensure
therapeutic effectiveness.
■
■
Monitor clinical response and clotting factor levels
regularly
to arrange to adjust dose as needed.
■
■
Monitor the person for any sign of thrombosis
to arrange to use comfort and support measures
as needed (e.g. support hose, positioning,
ambulation, exercise).
