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STROKE PREVENTION
Antiplatelet
Agents: mild blood thinners
Platelets are blood cells that are help the
blood clot (stick together) and prevent bleeding. When the
body has a cut, scratch, bruise, or bleed, platelets go
into action and begin to work. They can be thought of as
materials (like bricks or blocks) that aggregate (link together/
stack up) to form this clot. These platelet cells need thromoxane
A2, adenosine, vitamin K specific clotting factors (chemicals
produced by the body) to make them aggregate (stick) together.
These chemicals can be thought of as the glue that holds
the blocks together to make the clot. However, in patients
who have had a TIA or stroke, the blocks don’t need to stick
together as much because this causes the blood to be too
thick (like adding flour to milk when making a cake batter
it makes it thicker and harder to stir or pour) and possibly
form a clot that can’t fit through the vessels.
So, doctors often place stroke/TIA patients
on blood thinners to decrease the possibility of the body
forming another clot in the blood, which may lead to another
TIA or stroke.
Aspirin
- Aspirin is used for prophylaxis of
TIA and/or stroke except in patients with an allergy to
aspirin or salicylates.
- The mechanism of action for aspirin’s
stroke prevention is the inhibition of prostaglandin synthesis
action to prevent the formation of platelet-aggregating
substance thromboxane A2
- The usual dose for this indication
in adults is 50 – 325mg/day. Aspirin should be taken with
food, milk, or large glass of water to decrease GI problems.
Monitor for signs of bleeding.
Aspirin and Dipyridamole - Aggrenox®
- Aggrenox® is used
to reduce the risk of stroke in patients who have had
a TIA or completed ischemic stroke due to thrombosis,
except in patients with hypersensitivity to dipyridamole
or aspirin.
- The mechanism for its antithrombotic
action is the additive antiplatelet effect of
the two drugs. The aspirin portion works the inhibition
of prostaglandin synthesis action to prevent the formation
of platelet-aggregating substance thromboxane A2, while
the dipyridamole inhibits adenosine uptake into erythrocytes,
endothelial cells, and platelets.
- One capsule (aspirin 25mg and dipyridamole
200mg) twice a day is the usual dose
in adults. The capsule should be swallowed whole (not
chewed or crushed), and can be taken with or without food.
Most patients experience a severe headache when initiating
therapy due to the vasodilatation of dipyridamole. The
headache should ease and resolve after the body adjusts
to the treatment. In the mean time, acetaminophen (Tylenol)
is the treatment of choice for the headache.
Clopidogrel - Plavix®
- Clopidogrel is used to reduce future
atherosclerotic events (stroke) in patients with a recent
stroke.
- The drug’s mechanism is it blocks the
adenosine phosphate (ADP) receptors, which prevents fibrinogen
binding to the receptor. This decreases the ability of
platelet adhesion and aggregation.
- The usual dose for stroke prevention
is 75mg once a day, and can be taken without food. It
may be used as an alternative to aspirin containing products
in patients allergic to aspirin or salicylates.
Clopidogrel and Aspirin
- The combination of clopidogrel and aspirin is used
to reduce future atherosclerotic events (stroke) in patients
with a recent stroke or patients who had a stroke while
on clopidogrel.
- The mechanism of action for each drug
is different. Clopidogrel blocks the adenosine phosphate
(ADP) receptors, which prevents fibrinogen binding to
the receptor, while aspirin inhibits prostaglandin synthesis
action to prevent the formation of platelet-aggregating
substance thromboxane A2.
- The usual dose is clopidogrel 75mg
tablet and an additional aspirin 325mg tablet a day. Patients
may need to take the medications with food, milk, or a
full glass of water to decrease GI problems. Do not dispense
in aspirin/salicylate allergic patients.
Ticlopidine - Ticlid®
- Ticlopidine is used in patients to
decrease the risk of stroke or the occurrence of another
stroke. However, due to its life-threatening rheumatologic
disorders, it should be reserved for patients refractory
to aspirin or allergic to aspirin.
- The mechanism of action is unique
among the antiplatelet drugs because it specifically increases
bleeding time.
- The usual dose is 250mg twice a day.
It should be taken with food to decrease stomach upset.
- Starting the second week of therapy and through the
third month of therapy, patients will need a complete
blood count with differential every two weeks. The peak
occurrence of thrombocytopenia (TTP) is 3-4 weeks after
starting the medicine, with peak occurrences of neutropenia
at 4-6 weeks, and aplastic anemia incidences after 4-8
weeks.
Oral Anticoagulant: stronger blood
thinners
Warfarin
- Coumadin®
- Warfarin is used for the treatment
and prophylaxis of pulmonary embolism, venous thrombosis,
and thromboembolic disorders, and to prevent recurrences
of TIA’s. In stroke patients, warfarin is most often used
to prevent a cardiogenic embolism due to atrial fibrillation.
- The usual therapy for the prevention
of a cardioembolic TIA or stroke in patient with atrial
fibrillation is long term oral anticoagulation with a
target international normalized ratio (INR) of 2.5 (range
of 2.0-3.0)
- Warfarin’s mechanism of action is
interference with hepatic synthesis of vitamin K-dependent
coagulation factors (II, VII, IX, and X). Foods high in
vitamin K inhibit the effects of warfarin. Once patient
is stabilized on warfarin, the patient should not change
dietary habits. The patient needs to maintain a consistent
amount of vitamin K (70-140mcg/day) in their diet. Foods
that are high in vitamin K include: leafy green vegetables,
pork and beef liver, and green teas. Patients should be
instructed to avoid large amounts of alfalfa, broccoli,
asparagus, Brussels sprouts, cauliflower, cabbage, kale,
spinach, watercress, lettuce, and turnip greens, and to
consult their pharmacist or doctor who monitors their
warfarin therapy.
- Patients beginning warfarin will need to have weekly
laboratory test done to evaluate and stabilize their therapy.
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Stroke Education
