C H A P T E R 4 8
Drugs affecting blood coagulation
767
Haemorheologic agent
Oxpentifylline (
Trental
) is known as a haemorrheologic
agent, or a drug that can induce haemorrhage. It is a
xanthine that, like caffeine and theophylline, decreases
platelet aggregation and fibrinogen concentration in the
blood. These effects can decrease blood clot formation
and increase blood flow through narrowed or damaged
vessels. The mechanism of action by which oxpentifyl
line does these things is not known. It is one of the very
few drugs found to be effective in treating intermittent
claudication, a painful vascular problem of the legs.
Because oxpentifylline is a xanthine, it is associated
with many cardiovascular stimulatory effects; people
with underlying cardiovascular problems need to be
monitored carefully when taking this drug. Oxpenti
fylline can also cause headache, dizziness, nausea and
upset stomach. It is taken orally three times a day for at
least 8 weeks to evaluate its effectiveness. See Table 48.1
for additional information about this drug.
■■
To keep blood from coagulating, anticoagulants
block blood aggregates or interfere with the
mechanisms that cause blood to clot.
■■
Thrombolytic drugs activate the plasminogen system
to dissolve clots naturally.
KEY POINTS
DRUGS USED TO CONTROL BLEEDING
On the other end of the spectrum of coagulation
problems are various bleeding disorders. These include
the following:
•
Haemophilia
, in which there is a genetic lack of
clotting factors that leaves the person vulnerable to
excessive bleeding with any injury.
•
Liver disease
, in which clotting factors and proteins
needed for clotting are not produced.
•
Bone marrow disorders
, in which platelets are not
formed in sufficient quantity to be effective.
Bleeding disorders are treated with clotting factors
and drugs that promote the coagulation process. These
include antihaemophilic agents and haemostatic agents
(systemic and topical). (See Table 48.4.)
A
ntihaemophilic agents
The drugs used to treat haemophilia are replacement
factors for the specific clotting factors that are geneti
cally missing in that particular type of haemophilia.
These drugs include antihaemophilic factor, recombi
nant (
Recombinate
[not available in New Zealand]),
coagulation factor VIII (
Biostate
[not available In New
Zealand]) and factor IX complex (
MonoFIX-VF
).
TABLE 48.4
DRUGS IN FOCUS Drugs used to control bleeding
Drug name
Dosage/route
Usual indications
Antihaemophilic agents
Antihaemophilic
factor, recombinant
(Recombinate)
IV dose based on serum factor VIII levels and
body weight
Prevention and control of bleeding
episodes in haemophilia A; perioperative
management of bleeding in people with
haemophilia A
coagulation factor VIIa
(NovoSeven)
90 mcg/kg IV q 2 hours until haemostasis is
achieved
Treatment of bleeding episodes in people
with haemophilia A or B
factor IX complex
(MonoFIX-VF)
IV dose based on factor levels, weight and
desired response
Treatment or prevention of haemophilia B
(Christmas disease, a deficiency of
factor IX); treatment of bleeding episodes
in people with factor VII and factor VIII
deficiencies; controls bleeding episodes
in people with haemophilia A
Haemostatic agents
Topical
absorbable gelatin
(Gelfoam)
Smear or press onto surface; do not remove,
will be absorbed
Controls bleeding from surface cuts or
injury
human fibrin sealant
(Artiss, Tisseel)
Apply thin layer on to site
Adheres autologous skin grafts to
surgically prepared wound beds resulting
from burns in adults and children
