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Loss of Effect of Aspirin on Platelet Aggregation During Chronic Administration

This study has been terminated.
(Funding issue)
Information provided by (Responsible Party):
John Oates, Vanderbilt University Identifier:
First received: September 5, 2008
Last updated: April 10, 2017
Last verified: April 2017
Aspirin has shown to be beneficial to some patients with certain diseases such as coronary artery disease or stroke. We are investigating how aspirin works on regulating platelets and thromboxane over time at different doses. We hope to find the best dose of aspirin and/or other medications to help people who are at risk for heart attack or stroke.

Condition Intervention Phase
Platelet Aggregation Drug: aspirin Drug: placebo Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Basic Science
Official Title: Loss of Effect of Aspirin on Platelet Aggregation During Chronic Administration

Resource links provided by NLM:

Further study details as provided by John Oates, Vanderbilt University:

Primary Outcome Measures:
  • Comparison of platelet aggregation, serum thromboxane B2 (TxB2) levels, urinary thromboxane metabolite (Tx-M) levels, and urinary prostacyclin metabolite (PGI-M) levels over time and across dose ranges. [ Time Frame: 11 weeks ]

Enrollment: 51
Study Start Date: June 2004
Study Completion Date: February 2011
Primary Completion Date: February 2011 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: 1
ASA 40mg daily for 8 weeks followed by 3 weeks of observation
Drug: aspirin
40mg aspirin: one 40-mg aspirin capsule by mouth each morning + one Avicel capsule by mouth each evening
Other Names:
  • acetylsalicylic acid
  • ASA
Experimental: 2
ASA 1300mg daily for 8 weeks followed by 3 weeks of observation
Drug: aspirin
1300mg aspirin: one 650-mg capsule by mouth twice daily
Other Names:
  • acetylsalicylic acid
  • ASA
Placebo Comparator: 3
Placebo: one Avicel (cellulose) capsule by mouth twice daily
Drug: placebo
Placebo: one Avicel (cellulose) capsule by mouth twice daily
Other Names:
  • Avicel
  • cellulose

Detailed Description:

he purpose of the study is to better understand the mechanism for failure of daily aspirin administration to prevent cardiovascular events in some at risk individuals. We seek to describe the effect of chronic aspirin administration at varying doses on platelet aggregation. This will help to define mechanisms for aspirin failure and to pursue possible alternative therapies in patients who fail to respond to aspirin therapy.

We hypothesize that (1) inhibition by aspirin (ASA) of ex vivo-induced platelet aggregation varies in a predictable time and dose dependent manner, (2) thromboxane and prostacyclin production is inhibited by ASA in a dose-dependent manner and remains relatively constant over time once maximal inhibition has occurred, and (3) granule secretion by platelets during induced aggregation is inhibited by aspirin acutely but this effect does not persist during chronic administration at high doses.


Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Males
  • Age 18-40 years
  • Non-smokers

Exclusion Criteria:

  • ASA/NSAID use previous 14 days.
  • Evidence of ASA/NSAID use within previous 14 days at baseline visit based on investigator interpretation of platelet aggregation and platelet secretion studies.
  • History of chronic NSAID use.
  • Currently taking NSAIDs, corticosteroids, or anticoagulants.
  • History of coronary artery disease, myocardial infarction, coronary artery bypass grafting, percutaneous angioplasty, diabetes mellitus or stroke.
  • History of gastric,duodenal, or esophageal ulcers or serious gastrointestinal bleed.
  • History of frequent headaches, pain syndrome, or other condition requiring frequent use of analgesics.
  • History of adverse reaction to ASA.
  • Initial platelet count <100K/µl or >500K/µl.
  • Initial hematocrit <35% or >50%.
  • Weight less than 110 pounds.
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Please refer to this study by its identifier: NCT00748371

United States, Tennessee
Vanderbilt University
Nashville, Tennessee, United States, 37232-6602
Sponsors and Collaborators
Vanderbilt University
Principal Investigator: John A Oates, M.D. Vanderbilt University
  More Information

Responsible Party: John Oates, Professor of Medicine and Pharmacology, Vanderbilt University Identifier: NCT00748371     History of Changes
Other Study ID Numbers: GM15431-JAO1
Study First Received: September 5, 2008
Last Updated: April 10, 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No

Keywords provided by John Oates, Vanderbilt University:
platelet aggregation
granule secretion
thromboxane production
prostacyclin production

Additional relevant MeSH terms:
Anti-Inflammatory Agents, Non-Steroidal
Analgesics, Non-Narcotic
Sensory System Agents
Peripheral Nervous System Agents
Physiological Effects of Drugs
Anti-Inflammatory Agents
Antirheumatic Agents
Fibrinolytic Agents
Fibrin Modulating Agents
Molecular Mechanisms of Pharmacological Action
Platelet Aggregation Inhibitors
Cyclooxygenase Inhibitors
Enzyme Inhibitors
Antipyretics processed this record on August 17, 2017