A DHT blocker is a drug that blocks the formation of DHT, or dihydrotestosterone. DHT causes hair loss by restricting blood supply to hair follicles, causing the follicles to eventually die and fall out. The body naturally converts testosterone into DHT, and a DHT blocker helps prevent this process from happening. Men who use DHT blockers regularly see less hair loss as well as new hair growth in most cases. The two most well-known DHT blockers are dutasteride and finasteride.
Finasteride, marketed under the brand name Propecia, is approved by the Food and Drug Administration for the treatment of genetic male pattern baldness and hair loss. It works by inhibiting the activity of an enzyme called 5-alpha-reductase that is prevalent in the bloodstream of a man suffering from hair loss. By blocking the action of 5-alpha-reductase, finasteride thereby prevents the formation of DHT, helping prevent hair loss from occurring.
Dutasteride, under the brand name Avodart, works in much the same way as finasteride, by blocking the same enzyme 5-alpha-reductase. However, 5-alpha-reductase has two types: Type I and Type II. Finasteride blocks only Type I, while dutasteride blocks both types, reducing DHT formation by nearly 90 percent after two weeks of treatment. Dustasteride is therefore a stronger treatment than finasteride in the treatment of hair loss.