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Shaping a Research Agenda on Natural Product-Drug Interactions

August 09, 2013
Craig Hopp
D. Craig Hopp, Ph.D.

Program Director
National Center for Complementary and Alternative Medicine

View Dr. Hopp's biographical sketch

At NCCAM, one of the interesting things we are doing with respect to natural products is moving ahead on a plan for systematic evaluation of the ways in which they interact with prescription medications.

Numerous surveys have found that many people, particularly the elderly, take drugs and natural products (whether in the form of dietary supplements or foods) together. There is the potential for a wide range of effects—including mild to serious adverse events—from such combinations. As one example, St. John's wort has clinically significant interactions with many widely prescribed drugs, including birth control pills, anticoagulants, antiretrovirals, antidepressants, antiseizure drugs, and immunosuppressants. Interactions can affect drugs' concentrations in the body and hence their clinical effects. In light of the widespread availability and use of natural products, research on their safety (including interactions) is a major priority for NCCAM. At present, the data on interactions is very limited, highly variable, and mostly in the form of preclinical models, case studies, and hypothetical arguments.

Conducting research in this area is very challenging. There are an overwhelming number of supplements in the marketplace and a nearly infinite number of possible ways they can be combined with pharmaceuticals. Additional challenges include decisions about assays to use, appropriate patient populations for clinical studies, etc. NCCAM has been addressing these issues by:

  • Implementing a three-phase initiative for systematic in vitro and in vivo characterization of potential supplement-drug interactions
  • Forming an expert panel from the academic, research, and government communities and hosting two roundtable meetings, and
  • Developing, with the panel, criteria for decision making on substances to include in a testing matrix.

A report on the Dietary Supplement-Drug Interaction Expert Panel Meeting, held in April 2013, is now available online. Our goals are to not only bring the best science to the study of interactions, but to plan for disseminating those findings to the public and health-care providers so they can inform decisions on patient care. Now is also an opportune time to reiterate NCCAM's message on the importance of open patient-provider communication regarding complementary health approaches, including natural products, so that care can be as coordinated and safe as possible.


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My DO prescibed BenicarHCT for me to reduce my blood pressure.  I only use 2 other prescription meds…Singular and Ventolin but other supplements and herbs.  Using my Mediguard website I added the Benicar before starting to take it apprehensively as it was.  Since I also take Hawthorn because of MVP found this to be a high risk situation. I realize the problem associated with taking prescription drugs and supplements and herbs.  Hopefully there is a solution by more information available to the doctors and to the public.  I think anyone who does take supplements and herbs should be conscientious enough to be well informed about their situation. I much prefer to take my Hawthorn than the prescribed medication and wish my doctor would have easy access to interactions.    

I think people also should watch out for these MLM salesman and untrained doctors who recommend liver cleanses when people are on pain medications. The liver cleanses clear the drug faster, thus making the drug less effective, which can happen with other drugs as well, which can be a dangerous scenario.  Liver cleanses and other mixing of supplements and medications should be supervised by a medical doctor.-Dr.Christopher John Fiorentino

@Carol - Thank you for your comment. We agree that consumers must be conscientious in learning about any interactions of prescriptions drugs with supplements and herbs. We also advise consumers to check with their health care provider about drug-to-drug interactions and about any concerns they have related to the safety and effectiveness of  medications (both prescription and nonprescription). Tips for talking with a health care provider about complementary health approaches are available at  We also have resources for physicians that might be helpful.


Thank you for taking the opportunity to highlight the wonderful work of EarlyIntervention. Unfortunately, many do not realize the tremendous benefit of EI, butattention from officials like yourself, and social media really help to raise thepublics awareness. Thank you!

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