Side Effects Related to 5 α-Reductase Inhibitor Treatment of Hair Loss in Women: A Review

for dutasteride. The 7 studies that reported the existence of AEs also had a wide variation in dosing for both finasteride and dutasteride, suggesting that AEs during treatment may not be dose related. In contrast, it is of note that of these 7 studies, only 2 publications -- a clinical study and a retrospective review -- report that participants experienced changes in libido while taking finasteride for FPHL.^36,37 Both of these studies dosed patients with 5 mg of finasteride daily, for 12 and 18 months, respectively. Interestingly, none of the studies that used dutasteride as a treatment for FFA or FPHL reported decreased libido as a side effect. This is especially striking when one considers that dutasteride is considered the more potent 5 α-reductase inhibitor when compared with finasteride. Even more striking is the fact that post-finasteride syndrome in men has been recently added to the National Institutes of Health Genetics and Rare Diseases Information website.⁴⁵ This condition is characterized by “persistent sexual, neurological, and physical adverse reactions in patients who have taken finasteride…to treat hair loss… or enlarged prostate.”⁴⁶ From currently published literature on the use of these drugs in women for hair loss, it is unclear if these patients experience a similar constellation of symptoms.

Oliveira-Soares et al reported that 4 out of 40 postmenopausal patients experienced reduced libido as a side effect of finasteride treatment for FPHL, but that this was not perceived as a sufficient reason to stop treatment. This may not be the case for other women being treated with 5 α-reductase inhibitors for hair loss. While postmenopausal women are often concerned with changing sexual function during this stage of life,^24,42 FPHL and FFA patients may be more willing to accept a decreased libido as a side effect of treatment if hair maintenance and potential regrowth are possibilities of treatment with 5 α-reductase inhibitors. This may be a factor causing infrequent reporting of this side effect. Furthermore, it is unclear if patients from the studies reviewed here were being asked about any changes in sexual function or libido during their course of treatment with finasteride or dutasteride, or if they self-reported without prompting. This idea of an underreporting or underdetection of AEs related to sexual function is in keeping with a recent publication from Belknap et al that recently reported that safety reporting for 34 clinical trials of finasteride for the treatment androgenetic alopecia in males was inadequate when graded according to Ionannidis and Lau.²²

Some publications reviewed here did not include a list of all AEs that patients experienced. In this case, published reports may omit side effect information that clinicians may feel is important, leading to perpetuation of missed AEs. Women using 5 α-reductase inhibitors for hair loss should be encouraged to report any changes in sexual function after they begin treatment. Before starting treatment, clinicians should also tell patients that these changes are often influenced by other medical conditions, medications, and social factors,⁴⁷ and that they should be aware of the additional impact 5 α-reductase inhibitors can contribute to changes in sexual function. In addition, clinicians could present flibanserin, the recently