Finasteride pill (brand name Propecia) is one of the only two FDA approved products for hair loss treatment, the other being minoxidil. Topical finasteride has been explored by many users to lower side effects of finasteride pill. This blog will discuss (1) if the topical finasteride works, (2) whether its side effects is less than oral finasteride, (3) what is the best way to avoid side effects, and (4) how to make topical finasteride yourself. Finasteride powder

For topical finasteride to work, it needs to be able to lower the dihydrotestosterone (DHT) level in the scalp, meanwhile it shall have minimum impact on the serum DHT level to avoid any side effects.

In the 7th World Congress on Hair Research, a Dutch research group reported the effect of topical and oral administration of finasteride on DHT levels in the scalp and serum. Results showed the topical finasteride not only decrease the DHT level in the scalp but also in the serum. The good news is that topical finasteride decreases the scalp DHT level more than oral version does, meanwhile it has far less impact on the serum DHT level than oral finasteride. Thus the data supports topical finasteride works better than oral finasteride in two aspects: a) better hair growth; b) lower chance of side effects.
The results were confirmed by several clinical studies, In 2012, a Thailand group compared the efficacy and safety of the 24 weeks application of 3% minoxidil lotion (MNX) versus combined 3% minoxidil and 0.1% finasteride lotion (MFX) in men with AGA. Results show the MFX group had significantly greater improvement than the MNX group in the amount of hair regrowth, and no side effect was reported (see the details of this study below, study 2).

In 2009, an Iranian group compared the therapeutic effects of topical finasteride gel and tablet in treatment of male pattern hair loss, and found that the therapeutic effects of both finasteride gel and finasteride tablet were relatively similar to each other ( (see the details of this study below, study 3).
Table below shows the drug-Related Adverse Experiences for oral finasteride 1 mg (Propecia) after one year use in a large clinical study (Nearly 2000 participants). This is the data submitted and reviewed by FDA when Propecia was approved. As shown, the side effects of taking 1mg finasteide daily is slightly higher than the placebo group (Read the more detailed finasteide side effects here)

As the aforementioned data suggested that the systemic effect of topical finasteride is less than that of oral finasteride. It does not decrease the serum DHT level as much as oral finasteride. DHT is an important sex hormone. Lowering the serum DHT level is believed to be the cause of sexual side effects by finasteride (such as decreased libido, erectile dysfunction) . A lot of people including some hair loss professionals believe topical finasteride has zero sexual side effects, which is most likely untrue. Keep in mind that even placebo could cause side effects as shown in a large clinical study for oral finasteride. But there is little doubt that topical finasteride is much safer oral finasteride.