Effect of Primidone on Platelet Responsiveness in Patients Determined to be Clopidogrel Resistant

Inclusion Criteria: * Males and females aged 18 - 90 years who are clopidogrel resistant as determined by whole blood aggregometry * Patients with a low risk of new cerebrovascular ischemic events as indicated by an Essen Stroke Risk Score of less than three Exclusion Criteria: * Any history of allergy or intolerance to either Plavix or clopidogrel * Any history of allergy or intolerance to either Mysoline or primidone * Any clinically significant abnormalities in complete blood count as determined by the investigator * Use of any acute medications within the last two weeks or initiation of any non-study medications during the study period that would effect CYP enzymes or platelet function * Use of tobacco products from 2 weeks prior to enrollment in the study and throughout the duration of the study * Any planned surgical procedures during the study or 5 days after the study has ended * History of alcoholism or alcohol abuse * Participants who have had any alcohol consumption within 24 hours of a blood draw * Previous stroke in past 3 months * Participants who are or are planning to become pregnant * Participants who of reproductive potential must agree to use a method of contraception for the duration of the study as well as 4 weeks after participation is complete * Change in any medications that could affect liver enzymes or platelet aggregation throughout the study * Compliance less than 80 % based on pill counts on two different study visits