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.

You will receive

up to $1,375 for completing the study

You may be eligible to take part in this study if you

  • are 18-65 years old;
  • have been medically diagnosed with Type 2 diabetes and currently taking metformin (500-2550 mg daily), but otherwise healthy as determined by the study physician;
  • have an HbA1c < 8% as determined by laboratory analysis on initial screening;
  • are not taking any medications, dietary/herbal supplements, or citrus juices that can interfere with your ability to eliminate the study drugs and goldenseal;
  • are willing to abstain from consuming alcohol, caffeinated beverages or other caffeine-containing products the evening before and the morning of the first day of each study arm;
  • are female and are willing to use an acceptable method of contraception that does not include oral contraceptive pills or patches (such as abstinence, copper IUD, condom); and/or
  • have the time to participate.

You will not be eligible to take part in this study if you

  • have other chronic illnesses other than type 2 diabetes (eg., type 1 diabetes, kidney disease, hepatic disease, progressive coronary artery disease, chronic obstructive pulmonary disease, cancer, or HIV/AIDS);
  • have a hematologic (blood) disorder;
  • have a history of drug or alcohol abuse;
  • have any major psychiatric illness;
  • are female and are pregnant or breastfeeding;
  • have a history of allergy to midazolam or goldenseal products;
  • have a history of intolerance or allergy to midazolam or goldenseal; and/or
  • are taking concomitant medications, both prescription and non-prescription (including dietary supplements/herbal products) known to alter the pharmacokinetics of either study drug or goldenseal constituents.

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


The WSU Institutional Review Board has reviewed and approved this research project for human subject participation.