Finasteride is taken as a pill and works by inhibiting the 5-alpha-reductase enzyme responsible for producing DHT. Known more commonly by its brand name, Propecia, finasteride is only FDA-approved for men. In fact pregnant women should not even come into contact with finasteride as it can cause fetal deformities. Many men combine finasteride with an anti-inflammatory shampoo like Nizoral.
The longest clinical trial for a hair loss treatment was for the purposes of evaluating the efficacy of finasteride. In the 1990s, 1,553 men suffering from AGA were given daily one mg doses of finasteride or a placebo over a 12 month period. Each was allowed to enroll in the following one year trial extension, for up to five years. 1,215 men enrolled for the second trial extension, randomized to receive either finasteride or the placebo. Results showed significant hair regrowth for those in the blinded Finasteride group, as opposed to the placebo group. Baseline hair counts averaged 876 hairs in a 1” circle of scalp.
After the first year, finasteride patients averaged an extra 126 hairs in the same area over those taking the placebo. After five years this figure had increased to 277. Examiners recorded that 77% of those on finasteride showed increased hair regrowth after five years. This compared with only 15% in the placebo group.
A further two year trial concentrated on patients with frontal male pattern hair loss. 326 men with either frontal hair loss or thinning enrolled in the trial. Of these half had some vertex hair loss as well. After 12 months, those treated with finasteride showed a relative mean increase of 12 hairs in one cm² compared to those in the placebo group. The study concluded that finasteride slows hair loss and increases hair regrowth in the frontal scalp area.
Used in combination, finasteride really seems to increase hair regrowth for the first year or two. After that there is a more than a two thirds chance of it preventing any further hair loss. Like minoxidil, finasteride probably won’t reverse all hair loss, but for most it will at least stop it dead in its tracks.