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 Universitetshospital

December 6, 2005
December 7, 2005
January 28, 2014
January 2006
January 2008   (Final data collection date for primary outcome measure)
Myocardial infarction, Unstable angina, Cerebral infarction, Transitory cerebral ischaemia, Percutaneous or surgical vascular intervention, Sudden deterioration of symptoms, Amputation, Death. [ Time Frame: 5 years ]
  • Myocardial infarction
  • Unstable angina
  • Cerebral infarction
  • Transitory cerebral ischaemia
  • Percutaneous or sugical vascular intervention
  • Sudden deterioration of symptoms
  • Amputation
  • Death
Complete list of historical versions of study NCT00262561 on Archive Site
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Resistance to Aspirin and/or Clopidogrel Among Patients With PAD.
Prevalence of Resistance to Aspirin and/or Clopidogrel Among Patients With PAD. Prognostic Significance of Resistance to Aspirin

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.

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.

Phase 4
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Diagnostic
Intermittent Claudication
Drug: Aspirin
The effect of Aspirin on platelet function was assessed.
Active Comparator: Aspirin
All participants get Aspirin, and platelet reactivity measurements are performed.
Intervention: Drug: Aspirin
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*   Includes publications given by the data provider as well as publications identified by Identifier (NCT Number) in Medline.
January 2008
January 2008   (Final data collection date for primary outcome measure)

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
Sexes Eligible for Study: All
18 Years and older   (Adult, Older Adult)
Contact information is only displayed when the study is recruiting subjects
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Esben Hjorth Madsen, Aalborg Universitetshospital
Aalborg Universitetshospital
Danish Heart Foundation
Principal Investigator: Nils Johannesen, MD Department of Vascular Surgery, Aalborg Hospital
Aalborg Universitetshospital
January 2014

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP