The generic form of the brand-name drugs Propecia and Proscar. Propecia is the 1mg tablet of finasteride used for the treatment of hair loss. Finasteride works to prevent hair loss by blocking the formation of dihydrotestosterone (DHT) by inhibiting the enzyme 5 alpha-reductase. Proscar is manufactured by Merck and is FDA approved for the treatment of benign prostate enlargement.