Antiplatelet therapy

Currently the effectiveness of antiplatelet therapy as means of stroke prevention has been scientifically proven. Antiplatelet therapy reduces the risk of stroke by 25% (cardioembolic therapy reduced the risk by by 60%). General risk of developing ischemic complications, such as ischemic stroke, myocardial infarction and peripheral arterial damages has been reduced as well regardless of the location of the initial damage. Prolonged use of antiplatelet drugs is justified for all subtypes of ischemic stroke: cardioembolic, atherothrombotic, hemodynamic, lacunar, and also in hemorheological micro-occlusion. Antiplatelet drugs are especially effective in cardioembolic and atherothrombotic pathologies./p>

Aspirin

Among all the preventative antiplatelet drugs, the most widely used one is acetylsalicylic acid (aspirin) It is considered a "gold standard" of stroke prevention. Aspirin inhibits the enzyme cyclooxygenase, which leads to disruption of the formation of platelet aggregation inducer, which produces vasospastic effects, such as thromboxane A2. Aspirin causes platelets to lose the ability to produce thromboxane for 7-10 days, which is a lifespan of platelets.

The effectiveness of acetylsalicylic acid for stroke prevention has been studied numerous times. A meta-analysis conducted within the framework of the Antithrombotic Trialists Collaboration allowed the scientists to state that aspirin reduces the risk of vascular diseases by 23%.

In 1998, a meta-analysis of 10 randomized trials was conducted. They were aimed to determine the effectiveness of this drug. The study showed that, comparing with placebo, aspirin reduced the risk of stroke, myocardial infarction and death from vascular pathologies by 13%. 150-300 mg /day of Aspirin taken during 48 hours after the stroke reduced the risk of recurrent disruption of blood circulation in the brain by 11%.

Despite the fact that aspirin effectiveness as a stroke preventative has been proven, the relevance of its use as a means of general prevention is still doubted. However, the Woman's Health Study showed that as a primary preventative, aspirin leads to some risk reduction in women (especially true for women over 65 years of age).

Numerous studies show that there is no differences in receiving high (500-1500 mg / day), low (75-150 mg / day) or medium (160-325 mg / day) doses of aspirin in terms of the efficiency. As a result, doctors prescribe daily doses of aspirin 325 mg and lower for secondary prevention. However,high doses of acetylsalicylic acid for preventative purposes have caused side effects affecting the gastrointestinal tract, as well as hemorrhagic disorders./p>

There are also other forms of side effects discussed. They are relatedto the possibility of proaggregant effects of aspirin on platelets: daily doses of 500 mg of aspirin can cause similar decreases and increases of aggregation, and a fixed dose of the drug is not sufficient enough to suppress the platelet aggregation. That`s why, a number of patients have to increase their dose of aspirin in order to achieve the optimal aggregation effect. In vitro inhibition of aggregation by 50% from the initial level and more is achieved only in half of the cases, in 20% of patients there can be a paradoxical effect.

As means of secondary prevention of stroke, doctors also use:

Ticlopidine

The drug is an antagonist of adenosine receptors. It blocks the ADP-dependent activation of the glycoprotein IIb / IIIa platelet of fibrinogen receptor. As a result, it has a dose-dependent antiplatelet effect. The effectiveness of ticlopidine in reducing the risk of a secondary stroke in patients who had TIA has been proven. In a prospective study which lasted 2 years, ticlopidine (500 mg / day) reduced the risk of vascular death or the development of a recurrent stroke by 30% compared with placebo. In the TASS study, ticlopidine when compared with aspirin showed higher efficacy in reducing the risk of non-fatal and fatal stroke. However, prolonged use of this drug is often accompanied by such side effects as rash, agranulocytosis, diarrhea, aplastic anemia, neutropenia, allergic reactions and thrombocytopenic purpura.

Clopidogrel

This drug is also used in the prevention of secondary stroke. Its advantages are:

• The medicine can be taken once a day at a dose of 75 mg;
• The drug has no clinically important interconnectedness with other medicines;
• The drug has a small number of side effects.

Several randomized trials have demonstrated the effectiveness of clopidogrel as a preventative method and showed that it has fewer side effects in comparison with aspirin..

Dipyridamole

This drug has multiple effects unlike the antiplatelet medicines listed above. The action mechanism of this drug is an increase in cAMP content in platelets and inhibition of the enzyme phosphodiesterase. Dipyridamole also inhibits the formation of thromboxane A2, stimulates the release of prostacyclin by endothelial cells, increases the concentration of adenosine in the blood and inhibits its recurrent attack. Adenosine increases the cAMP content in platelets and stimulates adenylate cyclase. As a result, dipyridamole has an antiadhesive, antiaggregant and vasodilating action. It activates angiogenesis and stimulates an increase in collateral blood flow.

The long-term use of dipyridamole in clinical practice allows to recommend this drug as an effective means of preventing the stroke. It is especially recommended in such situations:

• The patient has contraindications to taking aspirin;
• Bronchial asthma and obstructive bronchitis;
• There is no possibility to control hemostasis;
• There is a risk of hemorrhagic complications;
• Patient is more than 65 years old with poorly manageable arterial hypertension. Simultaneous treatment with ACE inhibitors.

Practical indications for using new, modern and optimized form of this drug are:

• High risk of stroke;
• Prevention of thrombosis at any location;
• Prevention of stroke if there is low risk;
• Treatment of intermittent claudication;
• Angina pectoris in elderly patients;
• Prevention of stroke in elderly patients with atherosclerotic damage of cerebral vessels.

When creating strategy of general stroke prevention, antiplatelet therapy is justifiably considered an effective method of preventing new cases of strokes and other ischemic complications. Practical experience shows the need for early and long-term use of antiplatelet medicines.

Also see other articles on this topic:

• Green tea saves from a stroke
• Smoking and stroke
• Migraine and stroke

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