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Finasteride and Cutibacterium

Who can join

Ages 18 to 65 · Men · Healthy volunteers welcome

Inclusion We will include the group most impacted by PJI

* Adult males
* Age between 18 and 65 Exclusion
* History of cryptorchidism, hypospadias, or other congenital abnormality of male reproductive tract
* Female sex
* Age younger than 18 or older than 65
* Current use of Finasteride or other 5-alpha reductase inhibitors
* Current use of hormone replacement medications such as testosterone
* Recent antibiotic use within 3 months
* Have had a negative reaction to oral Finasteride before
* Recent use of acne treatment within 3 months
* Self-report very sensitive skin
* Allergic to chlorhexidine or isopropyl alcohol
* Have open wounds on both shoulders

About the study

High levels of Testosterone causes high amounts of skin bacteria (Cutibacterium Acnes) which can go into the skin during a shoulder replacement surgery and cause a terrible infection.

The goal of this experiment is to have participants take Finasteride, a medication that blocks testosterone production, for 2 weeks and evaluate the following:

* Blood levels of testosterone * Amount of bacteria on the skin.

Participants will:

* Be assigned to take Finasteride, or a placebo (a look-alike pill with no active medicine) once daily, for 2 weeks * Have a small sample of their blood collected and their skin swabbed with a Q-tip to determine Testosterone levels and bacteria on the skin * Blood draw and skin testing will take place before starting Finasteride or the placebo (day 0) and at the end of the experiment (day 14).

What is being tested

• Finasteride 5 mg (drug)
• Placebo Control (drug)

Sponsor: University of Washington · Participants: 40 · Started: Aug 31, 2026

Contact the study team

• Anastasia Whitson · Phone: 206-755-7847

Official record on ClinicalTrials.gov — NCT07731802

Locations in the U.S.

From ClinicalTrials.gov, data retrieved Nov 15, 2026. Each study sets its own eligibility; the study team decides who can join.