The Impact of Grapefruit Juice on the Response to Clopidogrel

This study will measure the percentage of platelet aggregation inhibition with a loading dose of clopidogrel (300 mg) using the VerifyNow Assay System in healthy volunteers who have drank 11 oz of grapefruit juice. It will also measure the percentage of platelet aggregation inhibition with a maintenance dose of clopidogrel (75 mg/day) using the VerifyNow Assay System in healthy volunteers who have drank 11 oz grapefruit juice daily.

This study will examine the effect of GFJ on the loading dose (300 mg) of clopidogrel and will evaluate the effect of GFJ on the maintenance dose (75 mg/day) of clopidogrel. Subjects will be randomized to either initially receive GFJ prior to their loading dose of clopidogrel or receive GFJ prior to their second loading dose. The subjects who have been randomized to receive GFJ initially will drink two small cans (11 oz total) of regular strength GFJ in the morning, followed two hours later by a loading dose (300 mg) of clopidogrel and will then return to the clinic 6 hours after their loading dose to have their platelet inhibition measured. Subjects will have ~ 5 milliliters (1 teaspoonful) of whole blood drawn from an antecubital vein in their forearm via a 21 gauge needle attached to a blue-top plastic vacuette sodium citrate blood collection (Greiner, Monroe, NC) tube to test inhibition of platelet aggregation. After their first loading dose, a 2 week washout period will follow to allow for their platelet aggregation to return to normal. Following the washout period, the subjects will take their second loading dose of clopidogrel and again return to the clinic for platelet inhibition measurement. The same timing will be followed for the loading dose taken without prior GFJ.

During the maintenance dose phase of this study, subjects will take 75 mg/day clopidogrel for 7 days with or without GFJ. Subjects will be randomized to either GFJ during the first period or GFJ during the second period. A minimum 2 week washout period will occur between the two 7 day courses of clopidogrel. Platelet inhibition measurement will occur at the end of each 7 day period as described above.

• Dietary Supplement: Grapefruit juice
  Participants received grapefruit juice during 1 of the 2 periods.
• Drug: Clopidogrel 75 mg/day
• Drug: Clopidogrel 300 mg

• Experimental: Loading Dose
  Participants received a 300 mg dose of clopidogrel with or without GFJ.
  Interventions:

  • Dietary Supplement: Grapefruit juice
  • Drug: Clopidogrel 300 mg
• Experimental: Maintenance Dose
  Participants received clopidogrel 75 mg/day for 7 days with or without GFJ
  Interventions:

  • Dietary Supplement: Grapefruit juice
  • Drug: Clopidogrel 75 mg/day

Inclusion Criteria:

• Ages 19-40
• Health status confirmed by medical history and physical examination and laboratory analysis

Exclusion Criteria:

• Pregnancy
• Taking routine prescription or over-the-counter prescriptions
• Taken over-the-counter analgesic/anti-inflammatory medication within two weeks of study participation
• Recently had grapefruit juice or regularly drinks grapefruit juice