Antiplatelets

Conditions treated

Antiplatelets are prescribed for a variety of conditions, including:

• Coronary artery disease. Antiplatelets may help to prevent a heart attack or stroke in patients who are at high risk of developing obstructive blood clots (coronary thrombosiscoronary thrombosis). Aspirin has been shown to prevent first heart attacks in middle-aged men who are asymptomatic and without any known heart disease. However, the recent CHARISMA study showed that certain antiplatelets do not provide a benefit to middle-aged people without known heart disease.
• Heart attack. An event in which the heart muscle does not receive enough oxygen-rich blood as a result of a blockage in the coronary blood vessels. Antiplatelets may reduce the damage to the heart if taken while an attack is in progress or immediately afterward (preferably within 30 minutes). Recent research also indicates that a combination of aspirin and other antiplatelets administered after a heart attack may reduce the risk of death, stroke or another heart attack.
• Angina. A temporary and often recurring chest pain, pressure or discomfort caused by inadequate oxygen-rich blood flow (ischemia) to some parts of the heart.
• Stroke. An event in which the brain does not receive enough oxygen-rich blood, usually due to blockage of a cerebral blood vessel by a blood clot. In high-risk patients, taking antiplatelets regularly has been found to prevent the formation of blood clots that cause first or second strokes. However, patients should not take aspirin or any other antiplatelet during a suspected stroke because it may cause further damage. Antiplatelets are contraindicated when the stroke is associated with brain hemorrhage or when the brain is likely to develop hemorrhagic transformation.
• Transient ischemic attacks (TIAs, or mini-strokes). A brief interruption of oxygen to the brain due to decreased blood flow through the arteries, usually because of an obstructing blood clot. Antiplatelet drugs have been found to be effective in the prevention of TIAs, and they also help prevent against ensuing strokes. TIAs are considered a major warning sign of impending stroke.
• Angioplasty. A catheter-based technique used to open arteries obstructed by a blood clot. Whether or not stenting is performed immediately after this procedure to keep the artery open, antiplatelets may reduce the risk of forming additional blood clots following the procedure(s). Aspirin and clopidogrel can reduce the chance of heart attack and death, especially if taken several hours before the procedure.
• Coronary bypass surgery. A surgical procedure in which an artery or vein is taken from elsewhere in the body and grafted to a blocked coronary artery, rerouting blood around the blockage and through the newly attached vessel. After the procedure, antiplatelets may reduce the risk of secondary blood clots.
• Atrial fibrillation. The most common type of sustained abnormal heart rhythm (arrhythmia), atrial fibrillation affects about 2 million Americans every year. During atrial fibrillation, the atria (the heart’s upper chambers) rapidly fire electrical signals that cause them to quiver rather than contract normally. This may lead to the creation of blood clots within the atria that can travel to the brain or other organs (embolism), potentially causing a stroke. Antiplatelets may reduce this risk. However, most patients with atrial fibrillation need to take anticoagulants because antiplatelets alone are not sufficient to reduce the risk of an embolism.

Conditions of concern

Patients should consult with their physician before taking antiplatelets. This is particularly important if an individual is allergic to aspirin or other analgesics. Also, antiplatelets may not be recommended if any of the following conditions apply:

• Impending surgery. Individuals who plan to undergo any surgical procedure requiring local, general or spinal anesthesia (including dental surgery) within two to three weeks. Surgery always carries the risk of uncontrolled and excessive bleeding, and antiplatelet medication could seriously increase that risk.
• Bleeding disorders. Antiplatelet medication could cause uncontrolled bleeding.
• Liver or kidney disease.
• Vitamin K deficiency (rare). Vitamin K is necessary to the natural formation of blood clots. Use of antiplatelet medication could potentially lead to uncontrolled bleeding.
• History of gastrointestinal bleeding or other bleeding problem.
• Thrombotic thrombocytopenic purpura (TTP). A rare, life-threatening blood disorder in which platelets are destroyed by antibodies. Antiplatelet medication could potentially lead to uncontrolled bleeding.

In addition, antiplatelets may make the following conditions worse:

• Anemia. A reduced number and or mass of red blood cells.
• Overactive thyroid. Overproduction of hormones by the thyroid gland, located in the front of the neck.
• Stomach ulcer. An open sore or crater in the stomach lining.

Side effects from antiplatelets may be increased in patients with the following conditions:

• High blood pressure (hypertension), which can increase the risk of bleeding into or around the brain
• Asthma
• Allergies
• Nasal polyps (or history of nasal polyps)

Potential side effects

Possible side effects of antiplatelet medication include:

• Allergic reaction (sneezing, respiratory congestion, swelling of throat, restricted breathing, itching or skin rashes)
• Nausea, indigestion or stomach pain
• Diarrhea

Adjusting when antiplatelets are taking may help reduce some side effects. For example, if the drug is taken after meals rather than on an empty stomach, it may reduce upset stomach and nausea. Patients are urged to contact their physician if they experience the side effects are severe, become worse or do not go away.

In addition, patients should contact their physician immediately if the experience:

• Unusual heavy bleeding (e.g., from a cut, during menstruation)
• Dark red or black, tarry stools
• Vomiting that looks like coffee grounds
• Coughing up blood
• Unusual bruising
• Feeling faint, dizzy or disoriented
• Ringing in the ears
• Chest pain or tightness in the chest
• Difficulty breathing
• Swallowing problems

Drug or other interactions

Patients should consult their physician before taking any other medication (either prescription or over-the-counter), nutritional supplements or herbal remedies. Some of these substances, such as cold medicine or antibiotics, can affect the way antiplatelets work. Non-steroidal anti-inflammatory drugs (NSAIDs) and medicines that contain aspirin may cause bleeding problems in individuals who take antiplatelets.

Lifestyle considerations

Patients should remember that antiplatelets can control many conditions, but cannot cure them. Even if all their symptoms are relieved, patients should continue to take their medication exactly as directed and to keep all scheduled follow-up appointments with their physician.

Patients taking antiplatelets or other anticoagulants may need to undergo regular blood tests to monitor their medication dosage. These tests usually require the patient to visit a hospital, physician’s office or laboratory on a monthly, bimonthly or weekly basis.

Approximately 5 to 10 percent of patients have been shown to have some type of platelet resistance. Preliminary evidence suggests that these people may be at higher risk of subsequent clotting events such as heart attack or stroke. It is not currently clear if a higher dose of antiplatelets can overcome these problems.

Regular use of some antiplatelets can add a significant amount of sodium to the diet. Patients adhering to a low-sodium diet may need to make further dietary adjustments when taking antiplatelets.

Pregnancy use issues

Taking antiplatelets in the last two weeks of pregnancy may cause bleeding problems in the baby both before and after delivery. When taken in the last three months of pregnancy, antiplatelets may prolong the length of the pregnancy and the delivery. Studies on antiplatelet use earlier in pregnancy have been inconclusive. Patients who are pregnant or are trying to become pregnant should inform their physician before taking antiplatelets. In general, aspirin should be avoided during pregnancy.

Antiplatelets can pass through breast milk to the infant. However, their effect on nursing infants is unknown. Parents should weigh the benefits and risks in consultation with their physician.

Child use issues

Children should never be given an antiplatelet unless under the direction of a physician. aspirin given to children under 15 has been linked to the onset of Reye syndrome, a potentially fatal inflammation of the brain. Whether other types of antiplatelets are safe for children has not yet been scientifically established.

Elderly use issues

Older adults report a higher frequency and intensity of side effects. Generally, older patients require lower doses of antiplatelets.