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Validation of an Assay to Measure Cyclooxygenase-1 Activity

Information source: Vanderbilt University
ClinicalTrials.gov processed this data on August 23, 2015
Link to the current ClinicalTrials.gov record.

Condition(s) targeted: Healthy

Intervention: aspirin (Drug); aspirin (Drug)

Phase: N/A

Status: Completed

Sponsored by: Vanderbilt University

Official(s) and/or principal investigator(s):
John A Oates, MD, Principal Investigator, Affiliation: Vanderbilt University


The purpose of this study is to obtain a reference range for a newly developed assay of ex vivo platelet COX-1 activity in normal volunteers taking a routine clinical dose of aspirin.

Clinical Details

Official title: Validation of an Ex Vivo Cyclooxygenase-1 Catalytic Assay in Humans

Study design: Allocation: Randomized, Endpoint Classification: Pharmacodynamics Study, Intervention Model: Parallel Assignment, Masking: Single Blind (Investigator)

Primary outcome: d8-thromboxane B2 generated in ex vivo platelet COX-1 catalytic assay

Secondary outcome:

Platelet aggregation by optical aggregometry

Serum thromboxane B2

Urinary 11-dehydro-thromboxane B2

Urinary prostacyclin metabolite

Detailed description: Aspirin has been shown to reduce cardiovascular events in at-risk individuals, but some aspirin-treated patients fail to exhibit expected changes in bleeding time and platelet aggregation. Recent evidence has correlated aspirin "non-response" to poor cardiovascular outcomes. In order to study the mechanisms of aspirin resistance, an assay is needed to measure the catalytic activity of platelet cyclooxygenase (which should be inhibited by aspirin). A common assay in general use is the measurement of thromboxane B2 production in clotting whole blood. This measure, however, is influenced by genetic and environmental variations in the glass-activated coagulation pathway, albumin binding capacity, platelet activation pathways, arachidonic acid pools, and phospholipase activity. Our laboratory has developed a direct assay of platelet cyclooxygenase (COX-1) activity that is not influenced by these variations. This study will generate a reference range in normal volunteers taking a routine clinical dose of aspirin (81mg daily) for this assay. In addition, by using two aspirin formulations (enteric-coated and chewable), the study design additionally allows the secondary comparison of the effects of these two formulations on COX-1 inhibition.


Minimum age: 18 Years. Maximum age: N/A. Gender(s): Both.


Inclusion Criteria:

- Non-smoker

- No chronic medical illness

- No chronic medications

Exclusion Criteria:

- Aspirin/NSAID use in preceding 14 days

- History of chronic NSAID use

- Currently taking NSAIDs, opioid analgesics, corticosteroids, or anticoagulants

- History of coronary artery disease, myocardial infarction, coronary artery bypass

grafting, percutaneous angioplasty, diabetes mellitus, or stroke.

- History of hypertension

- Body mass index > 35

- 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 reactions to aspirin

- Screening platelet count < 100,000/ul or > 500,000/ul

- Screening hematocrit < 35% or > 50%

- Weight less than 110 pounds

- Pregnant females

Locations and Contacts

Vanderbilt University, Nashville, Tennessee 37232, United States
Additional Information

Starting date: May 2007
Last updated: March 21, 2011

Page last updated: August 23, 2015

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