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Comment & Response
November 2017

Women Also Use 5α-Reductase Inhibitors—Reply

Author Affiliations
  • 1Department of Surgery, Western University, London, Ontario, Canada
  • 2Institute for Clinical Evaluative Sciences, London, Ontario, Canada
  • 3Department of Epidemiology and Biostatistics, Western University, London, Ontario, Canada
  • 4Division of Urology, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
JAMA Intern Med. 2017;177(11):1702. doi:10.1001/jamainternmed.2017.6090

In Reply Our article1 is indeed specific only to men taking this medication for benign prostatic hyperplasia. Unfortunately, our administrative data sources only have reliable prescribing information for people older than 65 years, thus we could not include the many younger men taking this medication at a lower dose for hair loss. Added to this limitation, we did not include the comparatively small number of women older than 65 years who may be using a 5α-reductase inhibitor for other indications (such as hirsutism or alopecia). Of the 799 997 prescriptions for a 5α-reductase inhibitor in 2015 in Ontario, only 0.04% (n = 302) were filled by women. Even if we did include them in our study,1 we would not have been powered to detect outcomes (which were only occurring among <2% of men) in this subgroup, which, as pointed out, could be very different based on gender. While there is certainly some evidence suggesting it may be used in women in certain situations, the product monographs for finasteride 5 mg or 1 mg and dutasteride 0.5 mg still state that use in women is contraindicated.2-4 We obviously support studies with maximal generalizability whenever feasible; however, in this case we feel limiting the study population to men was justified.

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