<p>CHD is the leading cause of death in the United States. One of the most common ways to prevent CHD is to take an anti-platelet agent,      which lessens platelet aggregation. Two of the most common anti-platelet agents are aspirin and clopidogrel. However, up to 25% to 30%      of people do not respond to these medications. Evidence indicates that treatment response may be related to genetics. The purpose of      this study is to determine specific gene variants that predict response to aspirin and clopidogrel therapy.</p>     <p>This study is part of a larger group of studies called the Pharmacogenomics Research Network (PGRN). Participants are from the      Old Order Amish of Lancaster, Pennsylvania. They are well suited for genetic studies because they are a homogenous, closed, founder      population. Participants received 300 mg of clopidogrel on the first day, then 75 mg of clopidogrel per day for the next 6 days. On      the last day of clopidogrel treatment, participants took a single dose of 324 mg aspirin. Participants underwent platelet function      tests before and after clopidogrel alone, and then again after taking clopidogrel plus aspirin. Using the gene variation profiles      across the genome, researchers analyzed which variants correspond to treatment response.</p>

Pharmacogenomics of Anti-Platelet Intervention (PAPI) Study

Association of cytochrome P450 2C19 genotype with the antiplatelet effect and clinical efficacy of clopidogrel therapy.