How do antiplatelet agents compare in acute coronary syndromes managed medically?

Acute coronary syndrome includes unstable angina and myocardial infarction. No head-to-head trials were found that directly compared different newer antiplatelet agents in patients with acute coronary syndrome managed medically only. But, there was no significant difference between clopidogrel plus aspirin and aspirin alone in mortality at 12 months [full review]. However, individuals taking clopidogrel plus aspirin had fewer myocardial infarctions but more major bleeding episodes. [full review]

How do antiplatelet agents compare in patients who have had coronary revascularization?

Coronary revascularization includes stenting and bypass grating. At 15 months following coronary revascularization and treatment with either prasugrel or clopidogrel:

• Prasugrel reduced the risk of repeat revascularization more than clopidogrel.
• Prasugrel and clopidogrel similarly reduced mortality due to all causes and due to a cardiovascular cause.
• There was more major bleeding with prasugrel than with clopidogrel but there was no significant difference in withdrawal rates due to adverse events. [full review]

Comparisons of clopidogrel with ticlopidine have found no significant differences in the risk of major bleeding at 28 days. Evidence suggests no difference in cardiovascular mortality at 30 days, and no differences in the need for revascularization for up to 6 months. [full review]

How do antiplatelet agents compare in preventing strokes or transient ischemic attacks?

Following a stroke or a transient ischemic attack (TIA), extended-release dipyridamole plus aspirin failed to demonstrate noninferiority compared to clopidogrel in reducing recurrent stroke [full review]. However, the risk of major bleeding and withdrawal due to adverse events is higher with extended-release dipyridamole plus aspirin [full review].

Compared with ticlopidine, clopidogrel similarly reduces mortality from all causes, cardiovascular mortality, and cerebral infarction over 52 weeks [full review]. The risk of major bleeding appears to be similar. The risk of neutropenia is lower with clopidogrel, and the overall withdrawal rate due to adverse events is lower. [full review]

How do antiplatelet agents compare in peripheral vascular disease?

No head-to-head trials were found that directly compared different newer antiplatelet agents in patients with peripheral vascular disease. However, compared with aspirin alone, there is no significant benefit with clopidogrel plus aspirin in reducing mortality or reducing the need for revascularization [full review]. In addition, there is no significant difference in the risk of major bleeding. [full review]

Does the duration of therapy influence the safety or effectiveness of antiplatelet agents?

No head-to-head trials were found that directly compared different newer antiplatelet agents based on duration of therapy. Compared to 1 month of treatment, after 6 months of treatment with clopidogrel plus aspirin, the risk of revascularization is lower, with no significant increase in the risk of bleeding. But, the benefit appears to decrease and no longer be significant by 8 or 12 months. [full review]

Does age, ethnicity or other illnesses influence the safety or effectiveness of antiplatelet agents?

Overall, there is insufficient data to determine whether one newer antiplatelet agent is superior when given to a particular age group, gender, race, or given to patients with other illnesses who are taking other medications.

In patients who are taking clopidogrel and are at an “average risk” of having a gastrointestinal bleed, the addition of a proton pump inhibitor (PPI) reduces the risk of being hospitalized due to a bleed. However, it remains unclear whether PPIs decrease the cardiovascular effectiveness of clopidogrel. [full review]

Drugs included in this review

Further Information

This PubMed Clinical Q&A was reviewed by Kimberly Peterson, MS.

For the full report and evidence tables, please see:
Ketchum K, Peterson K, Thakurta S, Low A, McDonagh M. Drug class review: Newer antiplatelet agents [Internet]. Portland (OR): Oregon Health & Science University; 2011 June. Available at http://www.ncbi.nlm.nih.gov/books/n/antiplatelets11/.