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Screening Herbs for Drug Interactions

This study has been completed.
Information provided by:
National Center for Complementary and Integrative Health (NCCIH) Identifier:
First received: January 9, 2002
Last updated: August 17, 2006
Last verified: July 2006
The purpose of this study is to detect potential herb-drug interactions in volunteers.

Condition Intervention Phase
Healthy Drug: herbals Phase 2

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Prevention
Official Title: R-21 Project: Screening Herbs for Drug Interference

Resource links provided by NLM:

Further study details as provided by National Center for Complementary and Integrative Health (NCCIH):

Estimated Enrollment: 140
Study Start Date: August 2001
Estimated Study Completion Date: May 2004
Detailed Description:

The use of herbal medicines in the treatment of various medical and psychiatric conditions has accelerated in the last decade. It has also become evident that herbal medications are being used concomitantly with conventional prescription and over-the-counter medications. However, the systematic evaluation of the potential of these agents to interact with conventional medications has been generally neglected. Compounding this problem is the fact that even single entity herbal products can contain a multitude of naturally occurring chemicals which serve as candidates for potential herb-drug interactions by inhibiting or inducing specific hepatic isozymes. Numerous reports document the importance of pharmacokinetic interactions involving inhibition or induction of the cytochrome P450 (CYP) enzyme system. In this study, the ten most commonly used herbal products in the US will be systematically evaluated for inhibition of CYP 3A4 and 2136, and induction of CYP 3A4. Collectively, these enzyme systems are involved in the metabolism of approximately 80% of all marketed medications.

Participants in this study will receive a single dose of the prescription drug alprazolam and the over-the-counter cough suppressant, dextromethorphan on two occasions. A combination of probe drugs will be given to normal volunteers both in the absence and presence of herbal medications. The plasma and urine concentration of these agents and their respective metabolites will be determined in order to evaluate individual herbal products degree and specificity of enzyme inhibitory or inductive effects.


Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Normal healthy volunteers who are taking no medications.
  • Must be non-smokers.
  Contacts and Locations
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Please refer to this study by its identifier: NCT00029263

United States, South Carolina
Institute of Psychiatry, Medical University of SC
Charleston, South Carolina, United States, 29425
Sponsors and Collaborators
National Center for Complementary and Integrative Health (NCCIH)
Principal Investigator: John Markowitz, MD Medical University of South Carolina
  More Information Identifier: NCT00029263     History of Changes
Other Study ID Numbers: R21AT000511-01 ( US NIH Grant/Contract Award Number )
Study First Received: January 9, 2002
Last Updated: August 17, 2006 processed this record on June 26, 2017