Propecia is a prescription medication primarily used to treat male pattern baldness, also known as androgenetic alopecia. It contains the active ingredient finasteride, which works by inhibiting the conversion of testosterone to dihydrotestosterone (DHT), a hormone linked to hair loss. By reducing DHT levels, Propecia can help slow hair loss and promote regrowth in some men. The medication is typically taken in pill form once daily and may take several months to show noticeable results. While Propecia is effective for many, it can cause side effects, including decreased libido and erectile dysfunction, which should be discussed with a healthcare provider.