A: Avodart (dutasteride 0.5mg) was approved by the FDA for the treatment of prostate enlargement in men in 2002. Avodart has not been approved for the treatment of androgenetic hair loss, although physicians can use an approved medication in ways other than for which it was specifically approved. That said, the use of dutasteride certainly requires a doctor’s supervision.

Like finasteride (the active ingredient in Proscar and Propecia), dutasteride blocks the enzyme 5-alpha reductase that converts testosterone to DHT (DHT is a key hormone that causes hair loss). However, unlike finasteride, which only inhibits the Type I form of the enzyme, dutasteride inhibits both the Type I and Type II forms. This combined effect lowers circulating DHT more with dutasteride than with finasteride, but also increases the incidence of its side effects.

The Type II form of the enzyme (blocked by finasteride) is found predominantly in the hair follicle. The Type I form of the enzyme has been found in the scalp and sebaceous glands, and many other parts of the body, but its exact role in hair growth has not been determined. It is felt that dutasteride’s ability to dramatically lower serum levels of DHT is what makes it a more potent medication in hair loss.

When considering the safety of dutasteride, one should consider the following:

• It acts on other parts of the body besides the hair follicle.
• Unlike finasteride, where families that had a deficiency of the Type II 5-alpha reductase enzyme were followed for years without any adverse effects, there is no natural biologic model to show the safety of dutasteride.
• Dutasteride has been approved for prostate enlargement in an older male population. It is not approved for hair loss and, in fact, the clinical trials for hair loss were discontinued, so there is no safety data for its use in younger patients. There is a greater incidence of sexual side effects with dutasteride compared to finasteride.
• The 1/2 life of dutasteride is 5 weeks compared to 6-8 hours for finasteride. Serum concentrations of dutasteride are detectable up to 4-6 months after discontinuation of treatment.

A: Propecia (finasteride 1mg) is not a prostate medication that was serendipitously noted to have a side effect of re-growing hair, it is a medication that was known all along that it might be able to slow hair loss and/or to grow hair.

Although finasteride was first approved for the treatment of prostate enlargement, the researchers at Merck knew, at the outset, that there were families whose members were deficient in the 5-alpha reductase, Type II enzyme and that the men in these families neither developed prostate disease nor went bald. In addition they had no long-term problems from the lack of this enzyme.

Merck used this natural model to develop a medication that could block the 5-alpha reductase, Type II enzyme – the result was finasteride. Because the only approved treatment for symptoms related to prostate enlargement at the time was surgery, Merck developed finasteride as a medical treatment for this condition prior to developing finasteride as a potential treatment for men with male pattern hair loss.

This also meant that Merck would understand the safety profile of finasteride, and have it approved for a medical disease (symptomatic prostate enlargement), before developing it for a cosmetic condition.

The drug was first submitted to the FDA for the treatment of prostate enlargement as Proscar (finasteride 5mg) in 1991 and it was approved for this use in 1992. The drug was submitted for the treatment of men with male pattern hair loss as Propecia (finasteride 1mg) in 1996 and was approved for this use in 1997.

A: Although there are many different causes, the overwhelming number of people that have hair loss have what is referred to as “patterned hair loss” or “androgenetic alopecia.”

In men, it is due to a hormone called DHT, which is a by-product of testosterone produced by the action of the enzyme 5-alpha reductase. This enzyme is inhibited by the hair loss medication Propecia. See the causes of hair loss in men page on the Bernstein Medical – Center for Hair Restoration website for more information.

In women, the mechanism is a little bit more complex as another enzyme, aromatase, is involved in the metabolic pathway. See the causes of hair loss in women page on the Bernstein Medical – Center for Hair Restoration website for more information.

We know that the inheritance comes from both the mother’s and father’s side, although the actual genes causing hair loss in men and women have not yet been identified. Statistically, the inheritance from the maternal side appears to be a bit stronger, but the reason for this is unknown.