Antiplatelets
Medications To Prevent Blood Clots

Anti-Blood Clotting Drugs

Preventing Blood Clots

Antiplatelets

Contents

What Are Antiplatelets?
When Is Aspirin Given?
When Is Clopidogrel Prescribed?
When Else Are They Needed?
What Are The Side Effects?
How Much Do Antiplatelets Cost?
Summary Of Antiplatelet Drugs
Summary of Treatment Choices


Main Guide:
Heart Disease in Women


Other Heart Drugs:

ACE Inhibitor Drugs
Anticoagulant Medications
Daily Aspirin Therapy
Beta Blockers
Calcium-Channel Blockers
Water Pills
Thrombolytics

Related Articles:

What is blood?
How does blood clot?

What Are Antiplatelets?

Antiplatelets are drugs which prevent blood clots from forming. Platelets are small cells in the blood which clump together to stop bleeding after a cut or injury. People with heart disease risk factors such as high cholesterol, hypertension, smoking or diabetes are prone to their platelets clumping together more easily. This can result in serious blood clots which are dangerous if they form in the arteries of the heart (leading to a heart attack) or brain (leading to stroke). In such instances the patient may receive the medication as a preventative treatment. If a person has received a diagnosis of coronary heart disease then one or more arteries will be partially blocked by the buildup of fatty deposits called atherosclerosis. As the arteries become narrow, blood flow has less space to pass through. If a blood clot suddenly forms and is caught in the narrowed passageway, blood flow is stopped and it can cause a heart attack or stroke, (depending on which artery is affected). Patients who have already had a heart attack or stroke are likely to be prescribed long-term antiplatelet therapy to reduce their risk of further blood clots and complications. The medications are also commonly prescribed to patients who have stents in their arteries inserted by coronary angioplasty. The most common antiplatelets are aspirin and clopidogrel (brand name Plavix).

When Is Aspirin Given?

Aspirin works by preventing platelets clumping together. When platelets become 'activated' they release several types of molecules, one of which is called thromboxanes. This particular molecule activates other platelets so that they all bunch together and form a clot. Aspirin sticks to a protein called COX (cyclooxygenase) which is needed to produce thromboxanes. By blocking the production of thromboxanes aspirin makes it harder for platelets to clot. This makes it less likely that someone will have a heart attack.

Aspirin therapy is a popular choice of treatment because it is cheap, effective and easy to take. It is usually the first heart attack treatment that patients take or are given. When a person dials 911 because they are experiencing a heart attack, emergency services advise them to take an aspirin while they wait. Taking aspirin during or directly after a heart attack can improve a person's survival rate by as much as 20 percent. When the patient arrives at hospital other antiplatelet medications may be administered orally or by IV. Additionally small doses of aspirin are recommended long-term for people at risk of heart attacks or stroke.

When Is Clopidogrel Prescribed?

This drug works in a similar way to aspirin by interfering with platelets ability to stick together and form clots. However, instead of blocking COX proteins, clopidogrel attaches to a receptor called adenosine diphosphate (ADP) which is on the outside of platelets. Like thromboxane, ADP activates platelets into sticking together, so by blocking ADP, clopidogrel makes it less likely that clots will form.

Most patients who are taking aspirin for a heart attack will also be given clopidogrel. It is not however given to patients who are likely to require coronary bypass surgery because of the risk of bleeding during surgery. Any patient who has had coronary angioplasty with a stent should also take clopidogrel for at least a year after the operation. Additionally, patients who cannot take aspirin (because of allergy reasons) but should, may also benefit from taking clopidogrel.

When Else Are They Needed?

Unstable Angina Pectoris
People who suffer angina attacks experience chest pain which is related to inadequate blood supply to the heart. This usually occurs as the result of severe blockages in the heart's arteries due to coronary heart disease. As these blockages occur gradually overtime, the angina symptoms slowly worsen over time. This is known as stable angina pectoris. Stable means that symptoms occur at predictable times, during times of exercise or physical exertion for example. When symptoms occur at rest or other unpredictable times, then it is categorized as unstable angina pectoris. Unstable angina indicates a more serious development of CHD. Platelet clumping is central to the development of unstable angina so patients diagnosed with it will usually be placed on antiplatelet meds.

Stents
If a stent is placed inside an artery to widen it (coronary angioplasty), some injury to the artery is inevitable. This means platelets can form at the point of injury to plug the tears. Injuries can occur in both patients who have received bare metal and coated stents. Patients who have bare metal stents are treated with aggressive antiplatelet therapy for at least a month after implantation. Aggressive antiplatelet therapy (or dual antiplatelet therapy) means using more than one antiplatelet at a time - for example, aspirin and clopidogrel or aspirin and ticlopidine. Those with coated stents are treated for longer (at least a year) because studies show they are associated with longer term risks of clots.

Coronary Artery Disease (CAD)
CAD is a type of CHD. Those who are diagnosed with CAD are usually placed on a daily dose of aspirin for life as a prophylactic measure to prevent heart attacks.

Peripheral Vascular Disease (PVD)
People who have PVD (that is blockages in the arteries of the legs as opposed to the heart) may be given the medication prophylactically.

Diabetics
As diabetes increases heart attack risk factors, diabetics may be recommended antiplatelets prophylactically.

What Are The Side Effects?

As with anticoagulants, the main risk of antiplatelets is bleeding - in particular, bleeding in the stomach. Antiplatelets (including aspirin) are not generally prescribed to patients who are currently bleeding in their stomach, intestines or other organs. Nor are they given to people with stomach ulcers.

High daily dosages of aspirin can cause kidney failure, but most patients will only be prescribed low doses, so this should not be a concern.

Because of possible drug interactions, patients should consult their doctor before taking nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen.

Other potential side effects include:
Tummy pain.
Heartburn or indigestion.
Nausea or vomiting.
Exhaustion.
Muscle pain.
Headaches.
Bowel disorders such as diarrhea or constipation.
A rash.

When To Call The Doctor

Severe side effects are rare, but if you experience any of the following, call your doctor immediately:

• Purple or red spots on the skin.
• Vision problems or loss of hearing.
• Blood in the urine or stools.
• Any unusual bleeding such as heavy periods or nose bleeds.
• Confusion or seizures.
• Vomiting accompanied by blood.
• Problems in swallowing.
• Dizziness or lightheadedness.
• Unexplained fever.

How Much Do Antiplatelets Cost?

The average monthly cost of taking:

1 clopidogrel (Plavix) tablet (75mg) daily is $220.
1 prasugrel (Effient) tablet (10mg) daily is $225.
2 ticlopidine tablets daily (250mg) is $65.
Dipyridamole (Aggrenox) combined with aspirin is $250.

1 daily aspirin is $1.

Summary Of Antiplatelet Drugs

Generic Name Brand Name Effectiveness in preventing heart disease in people with CHD Effectiveness in preventing stroke in patients who have had a stroke Effectiveness in preventing death in people with peripheral vascular disease (PVD) Increased risk of internal bleeding when combined with aspirin
Aspirin Bayers; Bufferin Yes Yes Yes N/A
Aspirin plus Clopidogrel Aspirin plus Plavix Yes No evidence Probably Yes
Clopidogrel Plavix Yes Probably Probably Yes

Summary of Treatment Choices

Health Condition Best Treatment Best Treatment if aspirin cannot be taken Less effective or less safe treatments Notes
Unstable angina or had heart attack Aspirin plus clopidogrel (Plavix) Clopidogrel (Plavix) Prasugrel (Effient); Aggreno; Ticlopidine Aspirin and clopidogrel should not be taken by people at high risk of stomach bleeding or stomach ulcers.
Stent implanted after angioplasty surgery Aspirin plus clopidogrel (Plavix) Clopidogrel (Plavix) Prasugrel (Effient); Aggreno; Ticlopidine Studies show benefits in combining drugs.
Had a stroke or transient ischemic attack (TIA) Aggrenox or aspirin or clopidogrel Clopidogrel (Plavix) Prasugrel (Effient) and Ticlopidine Aspirin alone is less effective than Aggrenox or clopidogrel.
PVD Aspirin Clopidogrel (Plavix) Prasugrel (Effient); Aggreno; Ticlopidine Studies suggest that clopidogrel and aspirin are as effective as each other.

  Related Articles on Antiplatelets

For more heart issues, see the following:

Risk Factors for Heart Disease
Heart Disease Testing
Living with Heart Disease

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