Effect of Testosterone Treatment on Drug Metabolism and Transport

April 27, 2026 updated by: Lauren Cirrincione, University of Washington

Effect of Gender-Affirming Testosterone Therapy on Drug Metabolism, Transport, and Gut Microbiota

This project will evaluate the effect of gender-affirming testosterone treatment on how other medications are processed by the body.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Gender-affirming hormone therapy may include testosterone, a hormone that the body creates and uses naturally. Testosterone is prepared as a medication that patients may take to increase hormone levels. Changes in testosterone concentrations in the body may affect how the body processes other medicines. The purpose of this study is to find out how testosterone therapy affects a single tracer dose of approved medicines in the blood (midazolam, digoxin, and acetaminophen) and to confirm testosterone treatment does not affect natural bacterial in the gut.

Study Type

Observational

Enrollment (Actual)

14

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Washington
      • Seattle, Washington, United States, 98195
        • University of Washington

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 60 years (Adult)

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Transgender adults planning to take testosterone treatment.

Description

Inclusion Criteria:

  • Self-identified trans* adult at least 18 years of age.
  • Not taking testosterone treatment currently.
  • Planning to start testosterone treatment through care provider for gender-affirming medical care.

Exclusion Criteria:

  • Unwilling/unable to return for project follow-up visits.
  • Unwilling/unable to provide written informed consent.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Cohort
  • Time Perspectives: Prospective

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
midazolam AUC ratio (treatment/control)
Time Frame: 0-48 hours
ratio of the area under of the plasma concentration time curve (AUC) of midazolam in the presence to absence of gender-affirming testosterone treatment.
0-48 hours

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
midazolam Cmax ratio (treatment/control)
Time Frame: 0-48 hours
ratio of the maximum plasma concentration (Cmax) of midazolam in the presence to absence of gender-affirming testosterone treatment
0-48 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Washington

Investigators

  • Principal Investigator: Lauren Cirrincione, MPH,Pharm D, University of Washington

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 1, 2021

Primary Completion (Actual)

February 15, 2024

Study Completion (Actual)

December 31, 2025

Study Registration Dates

First Submitted

October 15, 2021

First Submitted That Met QC Criteria

October 29, 2021

First Posted (Actual)

November 11, 2021

Study Record Updates

Last Update Posted (Actual)

May 4, 2026

Last Update Submitted That Met QC Criteria

April 27, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • STUDY00011644

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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