WHAT IS AN ANTIPLATELET MEDICATION?

Antiplatelet medications work on certain circulating blood cells in your body called platelets.  Platelets initiate the complex process of stopping bleeding from a cut or other injury.  In doing so, platelets stick together and form a plug. If this process is exaggerated the platelet plug becomes too large, and may totally block the flow of blood.  This can lead to a heart attack or stroke. Antiplatelet medicines reduce the chance of an unwanted blockage of blood flow occurring allowing the blood, which carries oxygen, to flow smoothly. 

WHAT ARE SOME EXAMPLES OF ANTIPLATELET MEDICATIONS?

Aspirin or ASA is the cheapest and most widely available antiplatelet medication.

Clopidogrel (Plavix™) and Ticlopidine (Ticlid™) are newer medicines that are in the same family of drugs.  Clopidogrel is used much more commonly than ticlopidine since it has fewer side effects.  These antiplatelet medicines may be used in combination with ASA, in people who are unable to take aspirin or in people who have had an unwanted blood clot while receiving aspirin.

Aggrenox™ is a combination product that contains two antiplatelet medicines (aspirin with extended release dipyridamole). It is used in those at risk for and who have had a mini-stroke or full stroke.  This is a special formulation, and is not the same as taking individual preparations of aspirin and dipyridamole together.

WHY DO I NEED AN ANTIPLATELET MEDICATION?

Antiplatelet medications are highly recommended in the following conditions:

• following a heart attack or an episode when heart damage could have occurred but was prevented by hospitalization, coronary angiography or the administration of clot dissolving drugs
• if you have had heart-related chest pain (called angina)
• following surgery on the blood vessels of the heart; that is, after bypass surgery
• following a procedure called angioplasty, especially if stents were placed within the blood vessels (arteries) of your heart
• following a mini-stroke (also known as a transient ischemic attack [TIA]), or a full stroke
• if you have excessive clogging of the main (or carotid) arteries in your neck
• following a procedure to clean out your clogged carotid arteries, known as carotid endartectomy

Antiplatelet medications may be beneficial in the following situations:

• if you have an irregular heartbeat (known as atrial fibrillation) and more intense anticoagulants either cannot be used or are not indicated
• in combination with blood thinners (or anticoagulants) for mechanical heart valves
• in those that are least 50 years of age and have at least one additional cardiac risk factor, such as high blood pressure, high blood cholesterol, smokers, etc.
• in those having blood circulation disease, known as peripheral vascular disease
• in other patients suspected to be at high risk of blood clots, including some patients with diabetes
•  

HOW DOES AN ANTIPLATELET WORK?

A stroke or heart attack occurs when a blood vessel providing oxygen is blocked by a plug or clot.  Antiplatelet medications work to prevent these plugs or clots from forming by preventing platelets from sticking together.

WHAT ARE THE RISKS / SIDE EFFECTS OF TAKING ANTIPLATELET MEDICATIONS?

All antiplatelet medications may cause you to take a little longer for bleeding to stop if you have a cut or injury.  You must inform your doctor right away if you experience any signs of serious bleeding, such as:  dark or bright red stool, red or pink urine, vomit looking bright red or like coffee grounds, severe headache or ‘stomach’ pain’(i.e., internal bleeding).

The most common adverse effect of aspirin is stomach upset. This occurs more often as the amount of aspirin taken increases (i.e., this effect is dose related).  Taking enteric-coated aspirin in the lowest available dose (usually 81 mg) may minimize this.  If this effect continues or worsens, bleeding can be a complication.  Other adverse effects reported with aspirin include heartburn, loss of appetite, or dizziness.  Medications that reduce the acid in your stomach, such as omeprazole (Losec™) may be appropriate to take with ASA if you have a history of stomach ulcers or are at risk for stomach bleeding.

Ticlopidine is used much less commonly today due to side effects that typically occur early in the course of therapy.  This includes diarrhea, nausea, and skin rashes.  A more serious side effect called neutropenia can interfere with your ability to fight infection.  Frequent blood tests, done every 2 weeks for the first 3 months, are necessary to identify this. This is usually reversible once it is detected and the medicine is stopped.  Most people taking ticlopidine today have been taking this medication for a long period of time and are now tolerating it well.

Aspirin with Extended Release Dipyridamole (Aggrenox™)

The most common side effects reported with Aggrenox™ are nausea, diarrhea, and stomach upset.  Headaches and dizziness have also been reported.  Most of these effects will go away as your body becomes used to this medicine.  If these effects continue or become bothersome, check with your doctor.

SHOULD SOME PEOPLE BE CAUTIOUS AND PERHAPS NOT TAKE ANTIPLATELET MEDICATIONS?

Certain conditions may warrant caution or avoidance of these medications.  These include:

• bleeding disorders
• low number of platelets
• active bleeding (for example, blood in the bowel movements). Note that antiplatelet agents do not routinely cause increased menstrual bleeding; unless periods are very heavy antiplatelet agents need not be stopped
• active or recently treated peptic ulcer disease
• allergy to the medication (symptoms of an allergic reaction may include a rash, itching, swelling, dizziness, trouble breathing)
• if you have a rare syndrome which includes asthma, rhinitis and nasal polyps – use of aspirin in such patients may result in a serious allergic reaction

HOW DO I TAKE MY ANTIPLATELET MEDICATION?

Aspirin

Take one tablet (amount usually ranges from 50-325 mg) once daily.  Taking Aspirin with food may reduce any stomach upset.  If you are taking the enteric-coated aspirin, swallow the tablet whole – do not crush or chew it.

Take one tablet (250 mg) twice daily, preferably with food to reduce nausea and stomach upset.

Take one tablet (75 mg) by mouth once daily, with or without food. 

Aspirin with Extended Release Dipyridamole (Aggrenox^â)

Take one capsule (Aspirin 25 mg with Extended Release Dipyridamole 200 mg) in the morning and one capsule at night, trying to separate them by 12 hours.  Take the capsule with water.  Swallow the capsule whole, not crushing it or chewing it.

HOW LONG WILL I HAVE TO TAKE ANTIPLATELET THERAPY?

When taking antiplatelet medicine to prevent blood clots, most people must take the medication indefinitely (unless otherwise specified).

DO I NEED TO HAVE ANY MONITORING DONE?

In general, routine blood tests are not necessary when you take antiplatelet medications (with the exception of ticlopidine).  However, your doctor may occasionally request a blood test to monitor your blood counts or other aspects of therapy.

WHEN SHOULD I CONSULT MY DOCTOR?

You should consult your doctor with any of the following:

• Signs of bleeding: blood coming from the mouth (vomiting up bright red blood or coffee-ground like material), the gastrointestinal tract (black stools or red in the stool), the nose, or if a severe headache or stomach pain develops, etc.
• Chest pain or discomfort (angina)
• Any symptoms of a mini-stroke or full stroke: loss of feeling or tingling on one or both sides of your body, a severe headache, sudden change in your ability to speak or to control movement of your body, etc.

ANSWERS TO COMMONLY ASKED QUESTIONS:

What should I do if I forget to take my antiplatelet therapy?

If you miss a dose, take it as soon as you remember.  If it is near the time of the next dose, skip the missed dose and resume your usual schedule.  Do not take two doses at once to catch up.

Is there ever a reason to take more than one antiplatelet medication?

Aspirin and clopidogrel are used in combination for patients having stents placed in the blood vessels supplying the heart (or coronary arteries).  Use of the combination may be for as short as 4 weeks to as long as a lifetime, with aspirin being continued lifelong.  This combination may also be used for some heart conditions.  It is important that this therapy is assessed periodically to ensure combination therapy is still necessary for you. Patients taking two antiplatelet agents have a higher risk of bleeding than those taking only one antiplatelet agent.

The combination product of aspirin and extended release dipyridamole (Aggrenox^â) is beneficial in those with cerebrovascular disease (stroke).

Is more aspirin better?

Aspirin 50 -325 mg daily is a usual dosage and is well tolerated.  There is not any benefit to taking more aspirin, and in fact, the risk of bleeding increases as the amount of aspirin increases.

If I need pain control, can I take more aspirin?

No! 

Be sure to carefully read all labels of any medicine that you can purchase without a prescription.  Pain relievers or fever reducers often contain medicine that will add to the antiplatelet effect of aspirin – many of them contain aspirin, non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin™), which can increase the risk of bleeding.  Ask your doctor or pharmacist to recommend a safe product for you.

Will I ever need to stop my antiplatelet medication temporarily?

You may be advised to stop taking your antiplatelet medicine 7 days prior to a surgical or dental procedure to prevent or reduce the chance of any bleeding during the procedure.  Always clarify this with your doctor or dentist.

For further information we suggest you consult the Heart and Stroke Foundation of Canada website (www.heartandstroke.ca)