Resistance to Aspirin and/or Clopidogrel Among Patients With PAD.

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00262561
Recruitment Status : Completed
First Posted : December 7, 2005
Last Update Posted : January 28, 2014
Danish Heart Foundation
Information provided by (Responsible Party):
Esben Hjorth Madsen, Aalborg Universityhospital

Brief Summary:

263 patients with peripheral atherosclerosis were examined to evaluate the activity of the platelets during the standard treatment, including aspirin. A subgroup of 43 received 600 mg of clopidogrel 2 h before platelet reactivity analysis.

The main hypothesis is that high platelet activity at the beginning of the study is associated with a higher risk of atherothrombosis. Follow up time is 5 years.

Condition or disease Intervention/treatment Phase
Intermittent Claudication Drug: Aspirin Phase 4

Detailed Description:

Patients with peripheral atherosclerosis are at high risk of atherothrombosis, mainly heart attack and stroke. The medical treatment of these patients include platelet inhibiting drugs, usually aspirin, to reduce the risk of ischemic events. Clopidogrel is another platelet inhibiting drug, which is prescribed less often, primarily because of the high costs compared to aspirin.

Phenomena of 'resistance' to these drugs have been described by numerous investigators. Essentially resistance means that the effect of the drug described is less than expected or missing, as measured by various laboratory methods. We do not know which way resistance is best described, but it has been described that patients who are 'resistant' to either drug are less protected against future heart attacks or strokes.

Main objectives:

  • To measure the activity of platelets in these patients during aspirin treatment.
  • To measure the activity of platelets in a minor population of these patients during clopidogrel treatment.
  • To evaluate the prognostic significance of resistance to aspirin in these patients.


Platelet activity is measured by the PFA-100 (Dade Behring) and by traditional turbidimetric aggregation.


Myocardial infarction, unstable angina, cerebral infarction, transitory cerebral ischaemia, sudden deterioration of symptoms, percutaneous or surgical vascular intervention, amputation, death.

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 263 participants
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Diagnostic
Official Title: Prevalence of Resistance to Aspirin and/or Clopidogrel Among Patients With PAD. Prognostic Significance of Resistance to Aspirin
Study Start Date : January 2006
Primary Completion Date : January 2008
Study Completion Date : January 2008

Resource links provided by the National Library of Medicine

U.S. FDA Resources

Arm Intervention/treatment
Active Comparator: Aspirin
All participants get Aspirin, and platelet reactivity measurements are performed.
Drug: Aspirin
The effect of Aspirin on platelet function was assessed.

Primary Outcome Measures :
  1. Myocardial infarction, Unstable angina, Cerebral infarction, Transitory cerebral ischaemia, Percutaneous or surgical vascular intervention, Sudden deterioration of symptoms, Amputation, Death. [ Time Frame: 5 years ]

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Atherosclerosis of the lower limbs, defined by one of the following criteria: Ankle-Brachial Pressure Index (ABPI)< 0.9, intermittent claudication, ischaemic pain at rest, ischaemic ulcers or gangrene.
  • Age > 18 years
  • For fertile women: Use of safe contraception (intrauterine contraceptive device, the pill, hormonal skin patches, progestogen injections, progestogen implant, vaginal ring)

Exclusion Criteria:

  • Allergy to either Aspirin or Clopidogrel
  • Known bleeding disorder
  • Platelet count < 140 mia/L or > 400 mia/L
  • Intake of NSAID's, SSRI's or Dipyridamol within the preceding 14 days
  • Not radically treated gastrointestinal ulceration within the last 6 month
  • Greater surgical procedures performed within the last 3 month
  • Severe renal disease
  • Severe hepatic disease
  • Breast feeding
  • Pregnancy

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00262561

Department of Vascular Surgery, Aalborg Hospital
Aalborg, Denmark, 9000
Sponsors and Collaborators
Aalborg Universitetshospital
Danish Heart Foundation
Principal Investigator: Nils Johannesen, MD Department of Vascular Surgery, Aalborg Hospital

Responsible Party: Esben Hjorth Madsen, M.D., Aalborg Universityhospital Identifier: NCT00262561     History of Changes
Other Study ID Numbers: 2005-003844-68
First Posted: December 7, 2005    Key Record Dates
Last Update Posted: January 28, 2014
Last Verified: January 2014

Keywords provided by Esben Hjorth Madsen, Aalborg Universityhospital:
Intermittent Claudication
Aspirin resistance
Clopidogrel resistance

Additional relevant MeSH terms:
Intermittent Claudication
Arterial Occlusive Diseases
Vascular Diseases
Cardiovascular Diseases
Signs and Symptoms
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
Purinergic P2Y Receptor Antagonists
Purinergic P2 Receptor Antagonists
Purinergic Antagonists
Purinergic Agents
Neurotransmitter Agents