Finasteride and Cutibacterium

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).

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