Dave001
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There was a small blinded placebo-controlled study of topical finasteride for hirsutism that has not previously been discussed here:
Price, T. M., S. Allen, et al. (2000). "Lack of effect of topical finasteride suggests an endocrine role for dihydrotestosterone." Fertility and Sterility 74(2): 414.
I do not have time to go into detail at the moment, but one of the salient outcomes is summarized by the following paragraph from the article referenced above:
"Finasteride is structurally similar to testosterone and DHT and is freely soluble in chloroform and alcohol. The potential for percutaneous absorption of finasteride exists on the basis of its steroid structure (2), resulting in a Food and Drug Administration warning that pregnant women should not even handle broken tablets. Our study suggests that topical application of finasteride does not result in significant systemic absorption. Despite daily application of 2.5–5 mg of topical finasteride, there was no increase in circulating testosterone or decrease in DHT levels over 6 months. This observation would have been strengthened by the ability to verify finasteride levels in the solution or in the circulation." (emphasis mine)
Everyone has been assuming that merely brushing up against a tablet of finasteride with uncovered skin would result in nearly complete systemic absorption of the drug. However, this is not supported by either one of the two small trials of topical finasteride for the treatment of hirsutism. The other study has been discussed here previously. It did not report serum hormone levels, but systemic exposure was assessed less precisely by comparing treated areas with untreated control areas of the skin.
I do not agree with the authors' explanations of the results from this study, but that is another matter.
Price, T. M., S. Allen, et al. (2000). "Lack of effect of topical finasteride suggests an endocrine role for dihydrotestosterone." Fertility and Sterility 74(2): 414.
I do not have time to go into detail at the moment, but one of the salient outcomes is summarized by the following paragraph from the article referenced above:
"Finasteride is structurally similar to testosterone and DHT and is freely soluble in chloroform and alcohol. The potential for percutaneous absorption of finasteride exists on the basis of its steroid structure (2), resulting in a Food and Drug Administration warning that pregnant women should not even handle broken tablets. Our study suggests that topical application of finasteride does not result in significant systemic absorption. Despite daily application of 2.5–5 mg of topical finasteride, there was no increase in circulating testosterone or decrease in DHT levels over 6 months. This observation would have been strengthened by the ability to verify finasteride levels in the solution or in the circulation." (emphasis mine)
Everyone has been assuming that merely brushing up against a tablet of finasteride with uncovered skin would result in nearly complete systemic absorption of the drug. However, this is not supported by either one of the two small trials of topical finasteride for the treatment of hirsutism. The other study has been discussed here previously. It did not report serum hormone levels, but systemic exposure was assessed less precisely by comparing treated areas with untreated control areas of the skin.
I do not agree with the authors' explanations of the results from this study, but that is another matter.
