Thank you for your interest in participating in the Goldenseal-Metformin Interaction Study.

We are no longer recruiting subjects. Enrollment is complete.

About the study:

The purpose of this research study is to determine whether goldenseal, a commercially available natural product, interferes with a protein in the gut that helps with metformin absorption, using midazolam as a probe to monitor for goldenseal effect. This study will consist of three study arms. During Arm 1, you will receive a single low dose of midazolam. During Arm 2, you will receive the same dose of midazolam plus a single dose of a well-characterized goldenseal product. During Arm 3, you will self-administer goldenseal three times daily for 27 days followed by the midazolam and goldenseal on the 28th day. Blood will be drawn from an intravenous catheter following administration of midazolam. Urine samples will also be collected. You will receive a screening medical exam and will undergo routine blood and urine laboratory tests prior to participating in the study. Roughly 50 hours of active participation (over the span of 5 weeks) is necessary to complete the study.


Learn more about The Center of Excellence for Natural Product-Drug Interaction Research at

The Washington State University College of Pharmacy and Pharmaceutical Sciences is conducting this research study through funding provided by the National Institutes of Health.


For more information about this study, please contact:

James Nguyen, Study Coordinator

Phone: (707) 813-1669