Thienopyridines

Thienopyridines

Thienopyridines such as ticlopidine (Ticlid) and clopidogrel (Plavix) inhibit the ADP receptor on the surface of platelets. Inhibiting the ADP receptors on the platelets prevent the platelets from aggregating and causing blood clots to form. The theinopyridines are more potent anti-platelet agents than aspirin. Clopidogrel (Plavix) is used far more commonly than ticlopidine (Ticlid) because ticlopidine can, in rare instances, cause low platelet and/or white blood cell counts.

Clopidogrel plays an important role in the treatment of heart attacks and is used in the following situations:

• Clopidogrel is used instead of aspirin in patients who have an allergy to aspirin.
• Clopidogrel often is given together with aspirin in treating heart attacks. Studies have shown that the combination of aspirin and clopidogrel is more effective than aspirin alone in improving survival and limiting damage to heart muscle among patients with heart attacks.
• Clopidogrel is given together with aspirin to patients undergoing PTCA with or without coronary stenting (see later discussion). Studies have shown that the combination of aspirin and clopidogrel is more effective than aspirin alone in preventing formation of blood clots that can re-occlude the coronary artery unblocked by PTCA and in preventing blood clots within recently placed stents.
• After a heart attack or after PTCA, aspirin is given indefinitely. The optimal duration of clopidogrel has not been established, and duration of use by physicians varies from weeks to months.

Patients who receive the combination of clopidogrel and aspirin are more likely than patients who receive aspirin alone to develop complications of major bleeding following coronary artery bypass surgery. Therefore, ideally clopidogrel should be stopped three to seven days before surgery.

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