A drug used to treat symptoms of an enlarged prostate gland. It is being studied in the treatment of male hair loss and prostate cancer. Dutasteride blocks enzymes the body needs to make male sex hormones. It is a type of 5-alpha reductase inhibitor. Also called Avodart and GG745. OR A synthetic 4-azasteroid compound with antiandrogenic activity. Dutasteride competitively and specifically binds to isoenzymes 1 and 2 of 5-alpha-reductase, forming stable enzyme complexes and inhibiting the conversion of testosterone to 5α-dihydrotestosterone (DHT); the reduction in DHT activity may mitigate or prevent enlargement of the prostate gland. The type 2 5-alpha-reductase isoenzyme is primarily active in the reproductive tissues while the type 1 isoenzyme is also active in skin and the liver.