C H A P T E R 4 8
Drugs affecting blood coagulation
765
this system breaks down fibrin threads and dissolves any
formed clot. The thrombolytics are effective only if the
person has plasminogen in the plasma. See Table 48.1
for usual indications for each of these agents.
Pharmacokinetics
These drugs are given IV and are cleared from the body
after liver metabolism. They cross the placenta, but it is
not known whether they enter breast milk (see Contra
indications and cautions).
Contraindications and cautions
The use of thrombolytic agents is contraindicated in
the presence of allergy to any of these drugs
to prevent
hypersensitivity reactions
. They should also not be used
with any condition
that could be worsened by the disso-
lution of clots
, including recent surgery, active internal
bleeding, cerebrovascular accident (CVA) within the last
2 months, aneurysm, vaginal or caesarean birth, organ
biopsy, recent serious GI bleeding, rupture of a non-
compressible blood vessel, recent major trauma (includ
ing cardiopulmonary resuscitation), known blood
clotting defects, cerebrovascular disease, uncon
trolled hypertension and liver disease (
which could
affect normal clotting factors and the production of
plasminogen
).
These drugs are also contraindicated in pregnancy
because of the possible adverse effects on the fetus or
neonate
. These drugs should not be used during preg
nancy unless the benefits to the mother clearly outweigh
the potential risks to the fetus. Caution should be used
during breastfeeding
because of the potential risk of
bleeding effects in the breastfeeding baby.
Adverse effects
The most common adverse effect associated with the
use of thrombolytic agents is bleeding. People should be
monitored closely for the occurrence of cardiac arrhyth
mias (with coronary reperfusion) and hypotension.
Hypersensitivity reactions are not uncommon; they
range from rash and flushing to bronchospasm and ana
phylactic reaction.
Clinically important drug–drug interactions
The risk of haemorrhage increases if thrombolytic agents
are used with any anticoagulant or antiplatelet drug.
■■
TABLE 48.3 Clinically important drug-drug
reactions with warfarin
↑
Bleeding effects
↓
Anticoagulation
↑
Activity and
effects of other drug
salicylates
barbiturates
phenytoin
chloral hydrate
griseofulvin
phenylbutazone rifampicin
disulfiram
phenytoin
chloramphenicol
carbamazepine
metronidazole
vitamin K
cimetidine
vitamin E
ranitidine
cholestyramine
cotrimoxazole
sulfinpyrazone
quinidine
quinine
oxyphenbutazone
thyroid drugs
glucagon
danazol
erythromycin
androgens
amiodarone
cefazolin
cefoxitin
ceftriaxone
meclofenamate
mefenamic acid
famotidine
nizatidine
Care considerations for
people receiving thrombolytic agents
Assessment: History and examination
■
■
Assess for any known allergies to these drugs
to prevent hypersensitivity reactions
. Also screen
for any conditions
that could be worsened by
the dissolution of clots
, including recent surgery,
active internal bleeding, CVA within the last
2 months, aneurysm, obstetrical delivery, organ
biopsy, recent serious GI bleeding, rupture of
a non-compressible blood vessel, recent major
trauma (including cardiopulmonary resuscitation),
known blood clotting defects, cerebrovascular
disease, uncontrolled hypertension, liver disease
(
which could affect normal clotting factors and
the production of plasminogen
) and pregnancy
or breastfeeding (
because of the possible adverse
effects on the neonate
).
■
■
Assess 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; and clotting
studies, renal and hepatic function tests, FBC,
guaiac test for occult blood in stool and ECG.
Implementation with rationale
■
■
Arrange to administer tenecteplase or streptokinase
to reduce mortality associated with acute MI
as soon as possible after the onset of symptoms
