Jump to content
panax quinquefolius Coumadin tablets garlic bulbs ginkgo leaves aspirin tablets St. John's Wort flower
An NIH Conference on Dietary Supplements, Coagulation,
and Antithrombotic Therapies
About this Conference
+ Conference Home
+ Purpose
+ Agenda
+ Sponsors
+ Proposal
+ Continuing Education
Conference Proposal

Purpose: The objectives of this workshop are to review the use of dietary supplements that have the potential to alter hemostasis and adversely effect antithrombotic medications and establish a framework for future development of clinical guidelines regarding dietary supplement use in patients on antithrombotic therapies. The workshop will also draft recommendations for new research opportunities in this area.

Background and History: The use of dietary supplements, which includes herbal remedies, vitamins, minerals, other botanicals, fibers, amino acids, proteins (including enzymes), organ tissues, and metabolites, is increasing in the United States. These products often contain ingredients that may either enhance or diminish effects of prescribed antithrombotic agents.

Long-term antithrombotic therapy is used for prevention and treatment of thromboembolism in patients with or at risk for cardiovascular and cerebrovascular diseases. Because these medications typically have a narrow therapeutic window, they must be monitored closely so that patients are not put at risk for thromboembolic or hemorrhagic complications.

Management of antithrombotic therapy is often complicated by drug interactions with other medications in a patient's drug regimen. The clinical significance of these interactions can often be predicted on the basis of known structural and metabolic characteristics of the drugs. However, drug interactions with over-the-counter (OTC) dietary supplements are much more difficult to characterize and predict because these products are not required to undergo FDA review or approval prior to marketing. Manufacturers are therefore not responsible for establishing their safety and efficacy. They also are not required to meet the same quality standards as licensed drugs. Although practitioners are encouraged to report such interactions to the FDA, published case reports of interactions with even the most widely used dietary supplements are limited. Currently, clinical guidance regarding supplement use for practitioners who prescribe antithrombotic medications and patients who receive them is lacking.

Scientific Importance: An estimated 4 million patients receive long-term antithrombotic therapies (anticoagulants and/or antiplatelet agents) and this number is expected to increase. Additionally, surveys suggest that dietary supplements may be used in 12-52% of the general population. Recently, 43% of VA ambulatory care patients reported using one or more dietary supplements, with up to 45% of supplement users having potential drug-dietary supplement interactions.

According to the Natural Medicines Comprehensive Database, approximately 180 dietary supplements have the potential to interact with warfarin and more than 120 may interact with aspirin, clopidogrel, or dipyridamole. They include anise and Dong Quai (anticoagulants effects); omega 3-fatty acids in fish oil, ajoene in garlic, ginger, Ginkgo, and vitamin E (antiplatelet properties); Fucus (heparin like activity); Danshen (antithrombin III-like activity and anticoagulant bioavailability properties), and St. John's Wort and American Ginseng (interference with drug metabolism). Others supplements, such as high dose vitamin E (vitamin K antagonist); Alfalfa (high vitamin K content); and Coenzyme Q10 (vitamin K-like activity) may affect vitamin K-dependent blood clotting.

In summary, although a variety of dietary supplements may affect hemostasis, very few are absolutely contraindicated in people with bleeding disorders or on antithrombotic therapy (anticoagulant and/or antiplatelet agents). The medical community would benefit from evaluation and information on these supplements and their harm or benefit to antithrombotic therapies.

Charge to the Panel

  • Identify factors that determine the beneficial or adverse effects of dietary supplements on hemostasis and antithrombotic therapies
  • Identify evidence that supports various effects of dietary supplements on hemostasis and antithrombotic therapies
  • Identify public health concerns about use of various dietary supplements; determine how they can be used safely by patients on antithrombotic therapies
  • Identify gaps in our knowledge on interactions of dietary supplements with antithrombotic therapies, and determine priorities of future research
  • Determine a framework for developing clinical guidelines on prescribing dietary supplements for patients on antithrombotic therapies and on recognizing, preventing, and monitoring their adverse effects.

Proposed dates of Event: January 13-14, 2005

Proposed Location: Masur Auditorium, Clinical Center, NIH Campus, Bethesda, MD

Organizer/Program Contact: Ahmed A.K. Hasan, M.D., Ph.D., Program Administrator, Thrombosis and Hemostasis SRG/BDP/DBDR/NHLBI, E-mail Address: hasana@nhlbi.nih.gov; Telephone Number: 301-435-0064; Fax Number: 301-480-1046.

Planned or Potential Outcomes: The proceedings will be published in a suitable medical journal to enhance public awareness, encourage standardization of methods used to assess the adverse effects of dietary supplements in individuals on antithrombotic therapies, and identify research needs.

Co-Sponsors: CC, NCCAM, NICHD, NINDS, ODS, ORD, and other NIH ICs.

Potential Participants: Stakeholders from academies and industries, representatives from Institutes and Centers within NIH, patient advocates, and members of other Federal (e.g., FDA) and non-governmental (e.g., United States Pharmacopoeia) regulatory and standards-setting organizations.

Agenda Summary

Thursday, January 13, 2005

Session I: Dietary Supplements That Affect Hemostasis and Antithrombotic Therapies

  • Interactions of dietary supplements with hemostasis
  • Epidemiology and inventory of supplements use by patients on antithrombotic (anticoagulant and/or antiplatelet) therapies

Session II: Biochemical Effects of Dietary Supplements on Hemostasis

  • Mechanisms of various effects of the supplements on hemostasis
  • Antithrombotic therapies

Session III: Clinical Data on Supplements Affecting Hemostasis and Antithrombotic Therapies

  • Evidence-based inventory of dietary supplements that are known to interact with anticoagulant, antiplatelet, and fibrinolytic agents

Friday, January 14, 2005

Session IV: Public Health Concerns: Facts, Fictions, and Gaps in Knowledge

  • Public health concerns regarding dietary supplement use while on antithrombotic therapies
  • Framework for developing clinical guidelines on prescribing dietary supplements for patients on antithrombotic therapies and recognizing, preventing, and monitoring their adverse effects

Session V: Panel of Experts: Opinions and Research Priorities; Develop Extensive Inventory of Supplements Affecting Antithrombotic Therapies

  • Gaps in our current knowledge for formulating a research agenda in the area

Session VI: New Tools and Emerging Technologies for Research and Monitoring

Session VII: Dialogue with Policy Makers


National Institutes of Health Department of Health and Human Services FirstGov, Your First Click to the US Government