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

This study has been completed.
Danish Heart Foundation
Information provided by (Responsible Party):
Esben Hjorth Madsen, Aalborg Universityhospital Identifier:
First received: December 6, 2005
Last updated: January 25, 2014
Last verified: January 2014

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 Intervention Phase
Intermittent Claudication
Drug: Aspirin
Phase 4

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: 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

Resource links provided by NLM:

Further study details as provided by Aalborg Universitetshospital:

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

Enrollment: 263
Study Start Date: January 2006
Study Completion Date: January 2008
Primary Completion Date: January 2008 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: Aspirin
All participants get Aspirin, and platelet reactivity measurements are performed.
Drug: Aspirin
The effect of Aspirin on platelet function was assessed.

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.


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
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Please refer to this study by its identifier: 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
  More Information

Responsible Party: Esben Hjorth Madsen, M.D., Aalborg Universityhospital Identifier: NCT00262561     History of Changes
Other Study ID Numbers: 2005-003844-68
Study First Received: December 6, 2005
Last Updated: January 25, 2014

Keywords provided by Aalborg Universitetshospital:
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 processed this record on April 21, 2017